C28 6628 3_OS_Rel_17_System_Control_Blocks_Nov68 3 OS Rel 17 System Control Blocks Nov68
C28-6628-3_OS_Rel_17_System_Control_Blocks_Nov68 C28-6628-3_OS_Rel_17_System_Control_Blocks_Nov68
User Manual: C28-6628-3_OS_Rel_17_System_Control_Blocks_Nov68
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File No. 5360-36 Form C28-6628-3 Systems Reference Library IBM System/3S0 Operating System System Control Blocks This publication shows the formats of the major control blocks and tables used by more than one component of the System/360 operating System control program. Descriptions of each field within the control blocks or tables follow each format illustration. The system control blocks described in this publication will be changed by IBM from time to time to extend the capabi1ities of the operating system. Programs should refer to these control blocks only through the system macro instruction facilities provided in the operating system. (For example, a field of the Data Control Block shou1d only be referred to by use of the DCBD macro instruction.) Programs that refer to the contr01 blocks by other means do so at the risk of not executing correctly in the future. OS Preface This publication contains reference information about the contents and format of system control blocks. Most of the control blocks covered in this publication are used by more than one component of the System/360 operating System control program. A diagram of each block is followed by descriptions of its fields. The block descriptions are ordered alphabetically by acronym. When a block has different access method versions, they are arranged under the block name in this order: SAM, I SAM, DAM, TAM, GAM. The pointer diagram previously shown in this publication has been superseded by a similar one now shown in the IBM publication IBM System/360 Operating System: Programmer's Guide to Debugging, Form C28-6670. The reader of this manual must be familiar with the following publications: IBM System/360: Principles of Operation, Form A22-6821 IBM System/360 Operating System: duction, Form C28-6534 Intro- IBM System/360 Operating system: Concepts and Facilities, Form C28-6535 IBM System/360 Operating System: Supervisor and Data Management Services, Form C28-6646 Fourth Edition (November, 1968) This is a major revision of, and obsoletes, C28-6628-2 and Technical Newsletter N28-2360. The changes in content made in this edition for this release are enumerated in a summary of revisions which follows the table of contents. Changes to the text, and small changes to illustrations, are indicated by a vertical line to the left of the change; changed or added illustrations are denoted by the symbol • to the left of the caption. This edition applies to release 17 of IBM System/360 Operating System and to all subsequent releases until otherwise indicated in new editions or Technical Newsletters. Changes are continually made to the specifications herein; before using this publication in connection with the operation of IBM systems, consult the latest IBM System/360 SRL Newsletter, Form N20-0360, for the editions that are applicable and current. Requests for copies of IBM publications should be made to your IBM representative or to the IBM branch office serving your locality. A form for readers' comments is provided at the back of this publication. If the form has been removed, comments may be addressed to IBM Corporation, Programming Systems Publications, Department D58, PO Box 390, Poughkeepsie, N. Y. 12602 @ Copyright International Business Machines Corporation 1966,1967,1968 Contents SUMMARY OF REVISIONS • 6 SYSTEM CONTROL BLOCKS MBBCCHHR - Actual Address Format • Revised Page Format communication Vector Table • Data Control Blocks Data Control Block QSAM. BSAM. BPAM. EXCP Access Method Data Control Block ISAM Data Control Block BDAM Data Control Block QTAM Data Control Block BTAM Data Control Block GAM Data Extent Blocks • Data Extent Block -- Ordinary Data Extent Block -- QTAM Message Processing Program • Data Event Control Blocks Data Event Control Block BSAM Data Event Control Block ISAM Data Event Control Block BDAM Data Event Control Block QTAM Data Event Control Block BTAM Data Set Control Blocks Data Set Control Block Format 1 Data set Control Block Format 2 Data Set control Block Format 3 Data Set control Block Format 4 Data Set Control Block Format 5 Data Set Control Block Format 6 Data Set Labels -- Magnetic Tape • Data Set Label 1 FLl Data Set Label 2 -- FL2 DEVICE NAME TABLE Event Control Block Interruption Control Block '. Input/Output Block • Job File Control Block • Line Control Block '. Partitioned Data Set Directory Entries • Partitioned Data Set Directory Entry General Format Partitioned Data Set Directory Entry Format 1 Partitioned Data Set Directory Entry Format 2 REQUEST BLOCKS Request Block -- PCP. MFT configurations • Request Blocks -- MVT configuration Interruption Request Block -- MVT Program Request Block -- MVT • System Interruption Request Block Supervisor Request Blocks -- MVT • Supervisor Request Block MVT Resident SVC Routines Supervisor Request Block -- MVT -- Transient SVC Routines Task Control Block • Task Input/output Table Uni t Control Block '. Volume Label • Volwne Table of Contents '. VOlwne Table of Contents '. 7 7 8 11 21 23 39 53 61 69 77 81 83 93 99 .101 .103 .107 .111 .113 .121 .123 .129 .135 .137 .141 .143 .145 .147 .151 .155 .159 .161 .165 .177 .189 .195 .197 .199 .203 .207 .209 .215 .217 ,.221 .225 .229 .231 .235 ,.239 .249 .253 .275 .277 .279 Illustrations Figures Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 1. 2A. 2B. 2C. 3. 4. 5. 6. 7. 8. 9A. 9B. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30A. 30B. 30C. 31A. 31B. 31C. 31D. 31E. 31F. 32. 33. 34. 35. 36. 37. · ··········· Communication Vector Table (Part 1 of 4) · Data Control Block - QSAM, BSAM, BP.Mi , EXCP - Device Type Segments Data Control Block - QSAM , BSAM. BPAM. EXCP - Foundation Segments Data Control Block - QSAM , BSAM , BPAM , EXCP - Access Method Segments Data Control Block - ISAM (Part 1 of 4) Data Control Block - BDAM (Part 1 of 2) Data Control Block - QTAM (Part 1 of 2) Data Control Block - BTAM (Part 1 of 2) Data control Block - GAM Data Extent Block Ordinary (Part 1 of 4) Data Extent Block -- QTAM -- Message Process Queue Data Extent Block -- QTAM -- Destination Queue Data Event Control Block BSAM .. II Data Event Control Block ISAlo1 10 Data Event control Block BDAM Data Event Control Block QTAM Data Event Control Block BTAM Data Set control Block Format 1 (Part 1 of 2) Data set Control Block Format 2 (Part 1 of 2) Data set Control Block Format 3 Data Set Control Block Format 4 Data Set Control Block Format 5 Data Set Control Block Format 6 Data Set Label 1 Data Set Label 2 Device Name Table Event Control Block Interruption Control Block Input/Output Block (Part 1 of 3) Job File Control Block (Part 1 of 2) .. JFCB Extension Block Line Control Block (Part 1 of 2) · · · PDS Directory Entry General Format PDS Directory Entry -- Format 1 PDS Directory Entry -- Format 2 Request Blocks -- PCP, MFT .. Interruption Request Block -- MVT Program Request Block -- MVT System Interruption Request Block -- MVT Supervisor Request Block -- Resident SVC Routines Supervisor Request Block MVT -- Transient SVC Routines Task Control Block (Part 1 of 2) Task Input/Output Table Unit Control Block (Part 1 of 3) The UCBTYP Field Volume Label Volume Table of Contents ···· ····· ······· · ··· ·· ··· ·· ·· · · '. · · · · ····· ·· · ··· ·· · · · · ···· ·· ·· · · · · ·· ·· ·· · ·· · · · · · · · · ·· ···· ···· ·· -- ···· ..·· · ···· · · ·· · · ·· · ···· · ····· ···· ·· · ·· ·· ·· · · · · ·· ··· ··· · ···· · · · · · · · · ·· · · ·· · · ·· · ····· · ······ · ·· ·· ·· · · ·· ·· · · ·· · ······ · ·· · · ·· · ····· ········· ···· · · ···· ·· ··· ·· ·· · · ·· · ·· · ···· 12 24 25 26 40 54 62 70 78 84 94 95 .102 .104 .108 .112 .114 .124 .130 .136 .138 .142 .144 .148 .152 .156 .159 .162 .166 .178 .187 .190 .198 .200 .204 .210 .218 .222 .226 .232 .236 .240 .250 .254 .265 .276 .278 ·· ·· ·· ·· · · · · · · · ·· · · · ...··· ·· ;~ Tables Table 1. Relation of BBCCHH Number to Devices 7 ( Summary of Revisions Subject Blocks or Fields Affected 2361 Core Storage DCBHIARC , JFCBHIAR, XSTAB, RBSTAB, XLIST, TCBMSS, TCBPQE World Trade Telegraph DCB-WTT Interface, DCBCPOLL, DECB-QTAM, BTAM, LCBINCAM, UCBTYP-Communications Advanced Checkpoint-Restart CVTCRTTR, CVTSTUSA, CVTSCTRK, JFCBTSDM, JFCBOTTR, JFCBMASK, JFCBIND2, JFCB + 96, XSTAB, TCBTRN Model 65 Multiprocessing CVTDCB, CVTMPCVT, TCBFLGS, UCBFL3 Variable Length Record Format Extension DCBRECFM, DCBLRECL, DCBPRECL, DS1RECFM, DS1LRECL, FL2RECL, FL2BLKA 2420 Model 7 Magnetic Tape unit SGJP, 1130-360 Data Transmission User Label in os Flush Data after DD DATA UCBTYP-Magnetic Tape Punch Check Recovery FORTRAN Use of IN-OUT Reduced Tape Error Recovery Read Opposite Work Disposition STAE Quiesce Abnormal Termination Time Slice Element Address - MFT, MVT SVC number format DECB - BSAM, BDAM Correction ECB - BSAM, BDAM, BISAM TIOT - Device is a Data Cell Drive TIOT - Device Entry Description TCB Format Change BTAM Field Names M= 1 GJP Model 91 ISAM Status Miscellaneous 6 OS System Control Blocks DCB-BTAM DS1EXT1, JFCBLTYP, VTOC CVTSTUSA DCBIND1 JFCBMASK DCBOPTCD, DEBOFLGS, JFCOPTCD UCBROR TIOELINK TCBNSTAE CVTXWTO CVTTSCE XRBNM DECTYPE CVTRELNO DECSDECB, DECBECB TIOEFSRT TIOT - Device Entry Description TCB DECB - BTAM. ECB - BTAM FL2TRTCW, FL2CNTR Device Address TCBFLGS, TCBTRN TCBTRN DCBST, DS2STIND DS1DSIND, DS1EXPDT , UCBTYP - Graphics., Deletion of TCBJSE, CVTIXAVL, DCBIFLG, TCBFLAGS., XSTAB, RBSTAB, DS4HPCHR, DCBBUFCT ( System Control Blocks System control blocks are the primary means for communicating information among the major parts of the System/360 Operating System control program. The information is stored in the control blocks and tables in a highly compact, readily accessible form. These blocks and tables have a standardized format, so that the information is usable by all parts of the control program. The addresses maintained in the control blocks and tables permit the control program to locate other control blocks and tables. If a field or block is used in different manners by the different configurations of the System/360 Operating System control program, the control program configurations are shown as: PCP - The primary control program configuration of the System/360 Operating System. MFT - The multiprogramming with a fixed number of tasks configuration of the System/ 360 Operating system. MVT - The multiprogramming with a variable number of tasks configuration of the System/360 Operating System. This publication consists of descriptions of the major system control blocks and tables. It illustrates their formats and describes their fields. Both the format illustrations and the field descriptions show the decimal (Dec.) and hexadecimal (Hex.) displacements of the fields. Each block description begins on a right-hand page for ease in turning to a particular block and to segment material about different blocks into sets of separate pages; thus, users may readily remove selected parts of the publication. MBBCCHHR - Actual Address Format In the operating system, the actual address for a location on direct-access storage is expressed in the 8 byte format MBBCCHHR. These 8 bytes contain: M - The extent number. A one-byte binary number specifying the relative location of an entry in a data extent block (DEB). Each extent entry describes a set of contiguous tracks allocated for the data set. For the first extent M=O except when ISAM is used. In that case, M=l for the first extent of user data. BB - The bin number. The number of the bin of a 2321 data cell drive, in which a data cell is mounted. (For devices other than 2321, this number is zero.) CCHH - The CCHH number. The number that identifies: • A track of a 2301 drum • • A subcell, strip, cylinder, and track of a 2321 data cell drive • • A cylinder and track of other direct-access storage devices. - The record number. The number of a record on its track. R Table 1 shows how the BBCCHH number relates to the various types of devices. Table 1. Relation of BBCCHH Number to Devices Device B B C C H 2301 Drum Track 2303 Disk Data Ce II Dri ve H Bin Subcell Cylinder Track Cylinder Track Strip Cylinder Track Note: Unused fields are zero. System Control Blocks 7 Revised Page Format The page format used to contain the control block field descriptions has been revised to that shown in the following: r---------------------------------------------------------------------------------------, I Bytes and Field Hex. I Offset Alignment Name Dig. Field Description, Contents, Meaning IL _______________________________________________________________________________________ JI The new format puts field identification data to one side of the page, and thereby gives major emphasis to describing the use of the field. The longer text lines make it easier and quicker to read and contrast successive field descriptions. The new format also includes a new item: alignment of the field with respect to the word boundary. When reading a dump, this helps to locate, for example, a flag field that is not the highorder byte of a word. For coding, it shows the relative position of the subject data or mask in a register. The columns of the new page format and their use are: Offset - The numeric address of the field relative to the beginning of the block. The first number is the offset in decimal, followed (in parentheses) by the hexadecimal equivalent. Example: 16 (10) Bytes and Alignment - The size (number of bytes) of the field and its alignment relative to the full-word boundary. Examples: 4 2 1 3 A 4-byte field beginning on a word boundary. - A 2-byte field beginning on a halfword boundary. - A 1-byte field in the low-order byte of a word. - A 3-byte field beginning at the low-order byte of a word (and running into the next word). Field Name - A name that identifies the field. This column is also used to show the bit settings of flag fields, that is, the state of bits in a byte. When the column is used to show the state of bits (0, 1) in a flag byte, it is shown as follows: x... 1... 0... •• xx The 8 bit positions (0 - 7) in a byte. For ease of scanning, the highorder (left-hand) 4 bits are separated from the low-order 4 bits. A reference to bit o. Bit 0 is on. Bit 0 is off • A reference to bits 6 and 7. Bit settings that are significant are shown and described. Bit settings that are not presently significant are described as reserved bits. Users should not use these bits because future features of the Operating system may make use of them. Hex. Dig. (Hexadecimal Digits) - The contents of the field expressed as hexadecimal digits .• Examples: F F 8 - 0 J K - 8 - A 1-byte field with all bits on. A 1-byte field in which the high-order bit has a meaning independent of the setting of the 4 low-order bits. - A 1-byte field in which the off-state of the 4 low-order bits has a significance independent of the state of the 4 high-order bits. - A general reference to the high-order 4 bits .• - A general reference to the low-order 4 bits .• os System Control Blocks Field Description, Contents~ Meaning - The use of the field. where a field's contents relate directly to a value coded by the user (generally in job control statements) the value coded is shown under the heading: Code - The value coded by the user that resulted in the described contents. POINTER DIAGRAM r---------------------------------------------------, I I I The pointer diagram previously shown here has been I I I superseded by a similar one now shown in the I IBM publication IBM System/360 Operating System: I I I Programmer's Guide to Debugging, Form C28-6628. IL___________________________________________________ I ~ System Control Blocks 9 ( Communication Vector Table The communication vector table (CVT) provides the means whereby nonresident routines may refer to information in the nucleus of the control program. The CVT is part of the resident nucleus. During the nucleus initialization process (NIP) the address of the CVT is placed in main storage in the full word at decimal address 16 (hexadecimal address 10). (Location 16(dec.)/10(hex.) points to the CVT but is not a part of the CVT. Figure 1 illustrates the format of the CVT. Descriptions of the fields follow the illustrations. The symbolic displacements shown for the various fields are generated in nonresident routines by use of the CVT macro instruction .• » CVT 11 COMMUNICATION VECTOR TABLE -4 (-4) CVTRELNO Reserved 0(0) CVTTCBP Pointer to Address for Next and Current TCB 4 (4) CVTOEFOO Address of Routine to Schedule Asynchronous Exits 8 (8) CVTLlNK Address of DCB for SYSl. LlNKLlB 12 (C) CVTJOB Address of Work Queue Control Blocks 16 (10) CVTBUF Address of Buffer for Resident Console Interruption Routine 20 (14) CVTXAPG Address of lOS Appendage Table 24 (18) CVTOVLOO Address of Entry-Point of Address Validity Checking Routine 28 (1C) CVTPCNVT Address of Entry-Point of Routine for Converting Relative Track Address to Absolute 32 (20) CVTPRLTV Address of Entry-Point of Routine for Converting Absolute Track Address to Relative 36 (24) CVTlLK1 Address of Channel and Control Unit Section in UCB Lookup Table 40 (28) CVTlLK2 Address of UCB Address List Portion in UCB Lookup Table 44 (2C) CVTXTLER Address of Entry-Point to XCTL Routine for Systems Error Routines 48 (30) CVTSYSAD Address of System Residence Volume Entry in UCB Table 52 (34) CVTBTERM Address of Entry-Point of ABTERM Routine 56 (38) CVTDATE Current Date in Packed Decimal 60 (3C) CVTMSLT PCP: Address of Master Scheduler Linkage Table MFT, MVT: Address of Master Scheduler Resident Data Area Continued • Figure 1. communication Vector Table (Part 1 of 4) ( 12 OS System Control Blocks COMMUNICATION VECTOR TABLE Continued 64 (40) Address of I/o CVTZDTAB Device Characteristic Table 68 (44) CVTXITP Address of Error Interpreter Routine 72 (48) CVTXWTO PCP: Address of Console Output Routine MFT, MVT: Address of System Quiesce Routine 76 (4C) CVTOFNOO Entry-Point Address to FINCH 80 (50) 82 (52) CVTBRET A BCR 15, 14 Instruction CVTEXIT An SVC 3 Instruction 84 (54) CVTSVDCB Address of DCB for SYS 1. SVCLlB 88 (58) CVTTPC Address of Pseudo Clock for Timer Routine 92 (5C) CVTPBLDL Address of BAL Entry-Point to BLDL Routine 96 (60) CVTSJQ Address of Selected Job Queue 100 (64) CVTCUCB Address of Tobie with Console UCB Address 104 (68) CVTQTEOO Address of Timer Enqueue Routine 108 (6C) CVTQTDOO Address of Timer Dequeue Routine 112 (70) Address of I/o CVTSTB Device Statistics Table 116 (74) CVTDCB System Configuration, Address of DCB for SYS1. LOGREC 120 (78) CVTlOQET Address of Request Element Table 124 (7C) CVTlXAVL Address of lOS Freelist Pointer Continued -Figure 1. Communication Vector Table (Part 2 of 4) CVT 13 COMMUNICATION VECTOR TABLE Continued 128 (80) CYTNUCB Lowest Storage Address Not in Nucleus 132 (84) CYTBOSY Address of Program Fetch Routine 136 (88) CYTODS Address of Entry-Point of Dispatcher 140 (8C) CYTILCH Address of Logical Channel Word Table 144 (90) CYTIERLC Address of Asynchronous Exit Queue 148 (94) CYTMSER PCP: Address of Major QCB MFT, MYT: Address of Master Scheduler Resident Data Area 152 (98) CYTOPTOl Address of Branch Entry-Point for Post Routine 156 (9C) CYTTRMTB Address of Terminal Table for QTAM 160 (AO) CYTHEAD Address of Highest Priority TCB in Ready Queue 164 (A4) CYTMZOO Highest Storage Address in Machine 168 (A8) CYTlEFOO Address of IRB Creation Routine 172(AC) CYTQOCR PCP: Reserved MFT, MYT: Address of a GFX Parameter List Word, or Zeros 176 (BO) CYTQMWR PCP: Reserved MFT, MYT: Address of Queue Manager's Communication Data Area 180 (84) 184 (B8) CYTSNCTR PCP, MFT, MYT: Serial Number Counter 182 (B6) PCP, MFT, MYT: Reserved PCP: CYTCRTTR - TTR of JCT for Restart ~ (BA) PCP: CYTSTUSA -------------------------------------------------MFT: CYTQCDSR - Reserved MYT: CYTQCDSR - Address of Search Routine for Contents Directory 188 (BC) _ _ _ _ -"CP:~YTSCTRK_ _ _ _ _ _ _ _ _.~O~E~ _ _ _ _ _ _PCP: Reserved _ _ _ _ _ _ _ _ PCP, MFT: CYTQLPAQ - Reserved MYT: CYTQLPAQ - Address of Top of Contents Directory in LPA Queue Continued -Figure 1. Communication Vector Table (Part 3 of 4) c 14 OS System Control Blocks COMMUNICATION VECTOR TABLE Continued 192 (CO) CYTMPCYT PCP, MFT: Reserved MYT: Address of M65MP Secondary CYT 196 (C4) PCP, MFT, MYT: Reserved 200 (C8) CYTABEND PCP, MFT: Reserved MYT: Address of Secondary CYT 204 (CC) CYTUSER PCP, MFT, MYT: Field Available to the User 207 (CF) MFT, MVT Extension 208 (DO) MFT, MYT: Reserved 212 (D4) CYTQABST MFT: Reserved MYT: An SYC 13 Instruction 216 (DC) -Figure 214 (D6) MFT, MYT: Reserved CYTTSCE MFT: Address of TSCE MYT: Address of First TSCE 1. 219 (DF) Communication Vector Table (Part 4 of 4) CVT 15 Offset 16 Bytes and Alignment Field Name COMMUNICATION VECTOR TABLE Hex. Dig. Field Description. contents. Meaning -4 (-4) 4 CVTRELNO Reserved. o (0) 4 CVTTCBP Address of a double word. the first containing the next-to-be dispatched TCB address. the second containing the last (current) TCB address. Both words are identical unless the task goes into a WAIT state. When in a WAIT state. the first word is set to zero until the waiting is over; then both words are once again identical. 4 (4) 4 CVTOEFOO Address of routine to schedule asynchronous exits. 8 (8) 4 CVTLINK Address of the DCB for the SYS1 .• LINKLIB data set .• 12 (C) 4 CVTJOB Address of work queue control blocks used by the job scheduler. 16 (10) 4 CVTBUF Address of the buffer of the resident console interrupt routine. 20 (14) 4 CVTXAPG Address of the I/O supervisor appendage table. 24 (18) 4 CVTOVLOO Address of entry point of the task supervisor's address validity checking routine. 28 (1C) 4 CVTPCNVT Address of entry point of the routine which converts a relative track address (TTR) to an absolute track address (MBBCCHHR). 32 (20) 4 CVTPRLTV Address of entry point of the routine which converts an absolute track address (MBBCCHHR) to a relative track address (TTR). 36 (24) 4 CVTILK1 Address of the channel and control unit portion of the UCB lookup table. 40 (28) 4 CVTILK2 Address of the UCB address list portion of the UCB lookup table. 44 (2C) 4 CVTXTLER Address of entry point of an XCTL routine that brings system error routines into the error transient area. 48 (30) 4 CVTSYSAD Address of the system residence volume entry in the UCB table. 52 (34) 4 CVTBTERM Address of entry point of the ABTERM routine. 56 (38) 4 CVTDATE Current date in packed decimal. 60 (3C) 4 CVTMSLT PCP: MFT.MVT: 64 (40) 4 CVTZDTAB Address of the I/O device characteristic table. 68 (44) 4 CVTXITP Address of the error interpreter routine. (48) 4 CVTXWTO PCP: MFT, MVT: (4C) 4 CVTOFNOO Address of entry point of the FINCH routine. OS System Control Blocks Address of master scheduler linkage table. Address of master scheduler resident data area. (compare the use of this field with the use of the CVTMSER field at offset 148 dec., 94 hex .• ) Address of the console output routine. Address of the system quiesce routine. ( Offset Bytes and Alignment Field Name COMMUNICATION VECTOR TABLE Hex. Dig. Field Description, Contents, Meaning 80 (50) 2 CVTEXIT An SVC 3 instruction (EXIT). 82 (52) •• 2 CVTBRET A BCR 15,14 instruction (used by data management routines). 84 (54) 4 CVTSVDCB Address of the DCB for the SYS1.SVCLIB data set. 88 (58) 4 CVTTPC Address of the 6-hour pseudo clockRead Punch Reader Punch Reader Read Punch Reserved PRINTER INTERFACE 16 (10) 1 DCBPRTSP Number indicating normal printer spacing .. Code xxx.. • xx. .. .. . 1 1 ... 1 ..... 1 •.. 1 ..... 1 1 ... 1 17 (11) • 1 DCBDEVT x.xx .. x.x .1 .... 1 ..... .. 1 ... 1 .. 1 .. 18 (12) ... 1 o 1 2 3 Device type. (Reserved bits> 1403 Printer and 1404 Printer (continuous form support only> 1443 Printer Test-for-printer-overflow mask (PRTOV mask). If printer overflow is to be tested for, the PRTOV macro instruction sets the mask as follows: xx •• xxxx ... 1. ... .. 1 19 (13) (Reserved bits) No spacing .. Space one line .. Space two lines • Space three lines • ••• 1 9 12 (Reserved bits) Test for channel 9 overflow • Test for Channel 12 overflow. Reserved END OF DEVICE INTERFACE SEGMENTS ( 30 OS System Control Blocks DATA CONTROL BLOCK -- SAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning COMMON INTERFACE 20 (14) 1 DCBBUFNO Number of buffers required for this data set. May range from 0 to a maximum of 255. 21 (15) • 3 DCBBUFCB Address of buffer pool control block. 24 (18) 2 DCBBUFL Length at buffer. May range from 0 to a maximum of 32,767. 26 (lA) •• DCBDSORG Data set organization to be used. Code 26 (lA) 2 Byte 1 IS PS DA 1 ••• • 1 •• • . 1. ••• x xx •• . . 1. ••• 1 PO U Indexed sequential organization. Physical sequential organization .• Direct organization• (Reserved bits) Partitioned organization • Unmovable - the data contains location dependent informationo Byte 2 27 (lB) GS 1 ••• .xxx xxxx 28 (lC) 4 DCBIOBAD Graphics organization. (Reserved bits) Address of the lOB when chained scheduling is used. FOUNDATION EXTENSION 32 (20) 1 DCBHIARC, DCBBFTEK, DCBBFALN Code x... • x •• 0 •••• 0 •• o. .. .1 •. 1. •. .0 .• .x.x .. 1.0 • 0.1 Buffer pool location. coded in the DCB macro instruction: Before Open none No choice made in the DCB macro instruction. After Open If no choice is made in the DD statement either (as shown by the JFCBHIAR field), the Open routine resets these two bits from 00 to 01. o Hierarchy 0 main storage. (See also: After Open. above.) 1 Hierarchy 1 main storage. S E •• x. x .•• 33 (21) • 3 • .xx • .10 •• 01 D • .11 F DCBEODAD F Buffering Technique: Simple buffering • Exchange buffering • (Reserved bits.) Buffer alignment: Doubleword boundary. Fullword not a doubleword boundary, coded in the DCB macro instruction. FUllword not a doubleword boundary, coded in the DD statement. End-of-data address. Address of a user-provided routine to handle end-of-data conditions. DCB - SAM 31 DATA CONTROL BLOCK -- SAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning FOUNDATION EXTENSION (Continued) 36 (24) 1 DCBRECFM Record Format Code 10 •• 01 •• 11 •• •• 1. ••• 1 1 ••• • 10. • 01. • 00. o •• 31 (25) • 3 Fixed record length. Variable record length. Undefined record length. U T Track overflow • B Blocked records • May not occur with undefined (U). Fixed length record format: Standard blocks. S (No truncated blocks or unfilled tracks are embedded in the data set.) Variable length record format: Spanned records. A ASA control character • M Machine control character • No control character • Key length (KEYLEN) was specified in the DCB macro instruction. This bit is inspected by the Open routine to prevent overriding a specification of KEYLEN= o by a nonzero specification in the JFCB or data set label. F V 1 DCBEXLST Exit List. Address of a user-provided list. FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM This 8 byte name must be the same as that appearing in the name field of the data definition statement which defines the data set associated with this DCB. It is used by the Open routine to locate the JFCB. 48 (30) 1 DCBOFLGS Flags used by the Open routine. 1 ••• 0 ••• . 1 •. •• 1. •.• 1 1 •.• • 1 •• .. o. .• 1. ••. 1 Last I/O operation was a WRITE. Last I/O operation was a READ or POINT. For direct-access devices, this means that the track balance field is invalid. Last I/O operation was in READ backward mode • Set to ! by EOV when it calls the Close routine for concatenation of data sets with unlike attributes. An OPEN has been successfully completed • Set to ! by a problem program to indicate a concatenation of unlike attributes. Tape mark has been read • Set to Q by an I/O support function when that function takes a user exit. It is set to 0 to inhibit other I/O support functions from processing this particular DCB. Set to 1 on return from the user exit to the I/O support function which took the exit. Set to 1 by an I/O support function if the DCB is to be processed by that function. ( 32 OS System Control Blocks DATA CONTROL BLOCK -- SAM Offset Bytes and Address Field Name Field Description, Contents, Meaning FOUNDATION SEGMENT -- BEFORE OPEN (Continued) 49 (31) • 1 DCBIFLG 00 •• 01 •• 11 •• •• 10 • • 01 00 •• 11 •• 01 •• 10 •• • .xx 50 (32) •• 2 DCBMACR Used by I/O supervisor in communicating error conditions and in determining corrective procedures. Not in error procedure. Error correction in process. Permanent error condition. Channel 9 printer carriage tape punch sensed • Channel 12 printer carriage tape punch sensed • Always use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. (Reserved bits.) Macro instruction reference. Major macro instructions and various options associated with them. Used by the Open routine to determine access method. Used by the access method executors in conjunction with other parameters to determine which load modules are required. EXCP ACCESS METHOD Byte 1 50 (32) Execute Channel Program (EXCP). Foundation extension is present with EXCP • Appendages are required with EXCP • Common interface is present with EXCP • (Reserved bits.) 1 •.. . 1 .. •• 1. ... 1 xxxx 51 (33) Byte 2 xxx x (Reserved bits.) Five word device interface is present with EXCP. Four word device interface is present with EXCP • Three word device interface present with EXCP. One word device interface is present with EXCP. 1 •.. . 1 .. o .1. · .. 1 BSAM - Input Byte 1 50 (32) 00 •• R •. 1. ••• x x •• x .1 .. · .1. 51 (33) Byte 2 00 •• . . 1. P C w ••• x • •• x 1 .... • 1 •• •• 1. L P C Always zero for BSAM • READ (Reserved bits.) POINT (which implies NOTE) • CNTRL BSAM - output Always zero for BSAM • WRITE (Reserved bits) Load mode BSAM (create BDAM data set). POINT (which implies NOTE) • CNTRL ) DCB - SAM 33 DATA CONTROL BLOCK -- SAM Offset Bytes and Alignment Field Name DC Bl-1'..ACR (Cont'd. ) Field Description, Contents, Meaning FOUNDATION SEGMENT -- BEFORE OPEN (Continued) Code Byte 1 50 o••• (32) • 1 •• G •• 0. • .• 1 1 ••. • 1 .. •• 1. •.• 1 51 Byte 2 0 ••• • 1 .. •• 0. (33) M L T C D P M • •• 1 1 ••. . 1 .. •• 1. L T C .•. 1 D (32) 00 •• •• 1. • 1 .• R READ P POINT (which implies NOTE) • (Reserved bits) ••• x x.xx Byte 2 51 (33) 000 • w •• 1. • 1 .• • •• x x. xx QSAM - Output Always zero for QSAM. PUT Always zero for QSAM • Move mode. Locate mode. Substitute mode • CNTRL Data mode • BPAM - Input Always zero for BPAM. Byte 1 50 QSAM - Input Always zero for QSAM. GET Always zero for QSAM • Move mode. Locate mode. Substitute mode • CNTRL Data mode • p BPAM - Output Always zero for BPAM. WRITE POINT (which implies NOTE) • (Reserved bits) FOUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT Offset from the TIOT origin to the TIOELNGH field in the TIOT entry for the DD statement associated with this DCB. 42 (2A) •• 2 DCBMACRF Contents and meaning are the same as those of the DCBMACR field in the foundation segment before OPEN. 44 (2C) 1 DCBIFLGS Contents and meaning are the same as those of the DCBIFLG field in foundation segment before OPEN. 45 (2D) • DCBDEBAD Address of the associated DEB. 3 Note: The above fields are overlaid on the DCBDDNM field during OPEN and are restored to their original form at CLOSE. 48 (30) 1 DCBOFLGS Contents and meaning are the same as those of the DCBOFLGS field in the foundation segment before OPEN. ( 34 OS System Control Blocks DATA CONTROL BLOCK -- SAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning ACCESS METHOD INTERFACE SEGMENTS EXCP ACCESS METHOD INTERFACE 49 (31) • 3 52 (34) 1 Reserved DCBOPTCD xxxx x.xx .1 •• Option Codes Code (Reserved bits) z Magnetic tape devices: Use reduced error recovery procedure. 53 (35) • 7 60 (3C) 2 DCBEOEA End-of-Extent Appendage ID (Identification) note). 62 (3E) •• 2 DCBPCIA Program-Controlled-Interruption Appendage ID (Identification) (See note). 64 (40) 2 DCBSIOA Start-I/O Appendage ID (Identification) 66 (42) •• 2 DCBCENDA Channel-End Appendage ID (Identification) 68 (44) 2 DCBXENDA Abnormal-End Appendage ID (Identification) note). 70 (46) •• 2 Reserved (See (See note). (See note). (See Reserved Note: The ID is that of an executable load module in the SVC Library. The module is loaded by the Open routine. Its address is placed into the appropriate slot in an appendage vector table constructed by the Open routine. If the ID is blank, its slot in the appendage vector table will contain the address of a return-point in I/O supervisor. BSAM, BPAM INTERFACE 49 (31) • 3 DCBREAD, DCBWRITE Address of READ or WRITE module .• 52 (34) 1 DCBOPTCD 1 .•• .1 •• •• 1. ••• x x. xx .1 •• » Option codes Code W Write validity check. U Allow a data check caused by an invalid character (1403 printer with UCS feature). C Chained scheduling using the Program Controlled Interruption. (Reserved bits) z Magnetic Tape Devices: use reduced error recovery procedure. 53 (35) • 3 DCBCHECK Address of the CHECK module. 56 (38) 1 DCBIOBL lOB length in double words. 57 (39) • 3 DCBSYNAD Address of user's synchronous error routine to be entered when a permanent error occurs. 60 (3C) 1 DCBCINDl x •• x xxx. • 1 •• •• 1. •.• 1 Condition Indicators. (Reserved bits> Search direct • Volume full or paper tape EOV • Exchange buffering supported • DCB - SAM 35 DATA CONTROL BLOCK -- SAM Offset 61 (3D) Bytes and Alignment • 1 Field Name Field Description, Contents, Meaning DCBCIND2 Condition Indicators 1 .... .. 1 ... •• 1 .. ••.1 1 ... .. • 1 .. .. •• 1 .. .... 0 Partitioned data set: STOW has been performed .. Sequential data set: Update. Direct organization data set: Last I/O was a write record zero. Sequential data set: UPDATE EOF is indicated .. PUT entered from Close while in Update mode (QSAM only) .. Permanent I/O error .. OPEN acquired buffer pool. Chained scheduling being supported .. FEOV bit (QSAM only) • Always set to Q for BSAM/BPAM .. 62 (3E) •• 2 DCBBLKSI Maximum block size. Maximum value: 32,764. For fixed-length blocked record format, it must be a multiple of the length given in DCBLRECL. For variable-length records, this must include the 4 byte block length field. 64 (40) 1 DCBWCPO write channel program offset.. Offset of write channel program from the start of the lOB. 65 (41) • DC BWCPL Length of Write channel program. 66 (42) •• 1 DCBOFFSR Offset of the Read CCW from the BSAM/BPAM prefix of the lOB. 67 (43) ••• 1 DCBOFFSW Offset of the Write CCW from the BSAM/BPAM prefix of the lOB. 68 (44) 4 DCBIOBA Normal scheduling: Address of BSAM/BPAM prefix of lOB .. Chained Scheduling: Address of ICB .. 72 (48) 1 DCBNCP Number of channel programs. Number of READ or WRITE requests which may be issued prior to a CHECK; the number of lOBs generated.. Maximum number: 99 .. 73 (49) • 3 DCBEOBR Address of the end-of-block module fo.r read .. 76 (4C) 4 DCBEOBW Address of the end-of-block module for write. 80 (50) 2 DCBDIRCI' For BPAM only: Directory count. Number of bytes used in last directory block.. range from 0 to a maximum of 254 .. 1 82 (52) •• 2 84 (54) 4 DCBLRECL May Logical record length. For fixed-length blocked record format, the presence of DCBLRECL allows BSAM to read truncated records .. DCBCNTRL, DCBNOTE, DCBPOINT Address of the CNTRL module or of the NOTE/POINT module .. ( 36 OS System Control Blocks DATA CONTROL BLOCK -- SAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning QSAM INTERFACE 49 (31) • 3 DCBGET, DCBPUT Address of GET module or PUT module. 52 (34) 1 DCBOPI'CD Option codes. Code 1 •• '. .1 •• W U •• 1. C ••• x x. xx .1 •• z Validity check. Allow a data check for an invalid character (1403 with UCS). Chained scheduling using the program controlled interruption. (Reserved bits) Magnetic tape devices. Use reduced error ~ecov ery procedure. 53 (35) • 3 DCBGERR, DCBPERR Address of the synchronizing routine for GET or of the synchronizing routine for PUT. 56 (38) 1 DCBIOBL lOB length in double words. 57 (39) • DCBSYNAD Address of the user's synchronous error routine to be entered when a permanent error occurs. 60 (3C) 1 DCBCINDl Condition Indicators. 3 1,. '•• • 1 •• •• 1. ••• x xxxx 61 (3D) • 1 DCBCIND2 1 ••• • 1 ... •• x • ••• 1 1 ••• • • 1,. •.• 1 2540 Card Punch: Data set was opened but no data was written. Search direct • Volume full· • (Reserved bits.) Condition Indicators. STOW has been performed. Last I/O was a write record zero • (Reserved bit) Permanent I/O error. OPEN acquired buffer pool. Track overflow in use • This is a QSAM DCB • 62 (3E) •• 2 DCBBLKSI Maximum block size. Maximum value: 32,764. For fixed-length blocked record format, it must be a multiple of DCBLRECL. For variable-length records this must include, 4 byte block length field provided by the access method .• 64 (40) 1 DCBWCPO Write channel program offset; offset of Write channel program from the start of the lOB.. 65 (41) • 1 DCBWCPL Length of Write channel program. 66 (42) ... 1 DCBOFFSR Offset of the Read CCW from the QSAM prefix of the lOB. 67 (43) '. '• • 1 DCBOFFSW Offset of the Write CCW from the QSAM prefix of the lOB .• » DCB - SAM 37 DATA CONTROL BLOCK -- SAM Offset Bytes and Alignment Field Name 68 ( 44) 4 DCBIOBA Normal Scheduling: Address of QSAM prefix of lOB. Chained Scheduling: Address of ICB. 72 (48) 4 DCBEOBAD End-of-buffer address. Address of last byte of the current buffer. 76 (4C) 4 DCBRECAD Address of the current or next logical record. 80 (50) 2 82 (52) •• 2 DCBLRECL Format F records: Record length. Format U records: Record length. Format V records Unspanned record format Record length. GET, PUTX: PUT: Actual or maximum rec0rd length. Spanned record format Locate mode Segment length. GET: PUT: Actual or minimum segment length. Move mode GET: Record length. PUT: Actual or maximum record length. Data mode, GET Data records up to 32,752 bytes: Data length. Data records exceeding 32,752 bytes: Before Open: X'8000'. After Open: Data Length. output mode" PUTX (output data set): Segment 1 ength. 84 (54) 1 DCBEROPT Error option. Disposition of permanent errors if the user returns from a synchronous error exit (DCBSYNAD), or if the user has no synchonous error exit. Reserved 1 •• '. .1. ,. •• 1. ••• x xxxx 38 Field Description, Contents, Meaning Code ACC Accept SKP Skip ABE Abnormal end of task • (Reserved bits) 85 (55) • 3 88 (58) 2 90 (SA) •• 2 DCBPRECL Format F records: Block length. Maximum block length. Format U records: Format V records Unspanned record format: Maximum block length. Spanned record format other than data mode, PUT: Maximum block length. Data mode, PUT: Data length. 92 (5C) 4 DCBEOB Address of the end of block module. DCBCNTRL Address of the CNTRL module. Reserved os System Control Blocks ( Data Control Block-ISAM This data control block (DCB> is used by the indexed sequential access-method (ISAM) routines and holds data pertinent to the use of a data set that is maintained by the ISAM routines. The common interface and the foundation sections serve the same purpose in all DCBs although the formats may vary slightly for different access method routines. Figure 3 illustrates the format of this DCB. Descriptions of the fields follow the illustration. ) DCB -- ISAM 39 DATA CONTROL BLOCK -- ISAM Device Interface 16 (10) DCBKEYLE 17 (11) DCBDEVT Key Length 18 (12) DCBTRBAL Track Balance Device Type 19 (13) Common Interface 21 (15) 20 (14) DCBBUFCB Address of the Buffer Pool DCBBUFNO Buffer Required 26 (1A) 24 (18) DCBDSORG Data Set Organization DCBBUFL Buffer Length 28 (lC) Reserved 31 (1F) Foundation Extension 32 (20) DCBHIARC, DCBBFTEK, DCBBFALN 33 (21) 36 (24) 37 (25) DCBRECFM DCBEODAD Address of EODAD Routine DCBEXLST Address of the Exit List Record Format 39 (27) Foundation 40 (28) DCBDDNAM DD Statement Data Set Name 50 (32) 49 (31) 48 (30) DCBOFLGS Open Routine Flags I/o DCBMACR Macro Instruction Code DCBIFLG Supervisor Flags 51 (33) After OPEN 40 (28) DCBMACRF Macro Instruction Code 45 (2D) 44 (2C) I/o 48 (30) 42 (2A) DCBTIOT Offset in TIOT Table to DD Entry DCBDEBAD Address of the DEB DCBIFLGS Supervisor Flags DCBOFLGS Open Routine Flags , , !... -- ...... -----------------------~------------------------------------------------------------------------------------------------------------_ ... _------ ... ------ ..... - ... ------------------------- ... _----------------: Access Method Interface - ISAM 49 (31) DCBGET, DCBPUT Address of GET or PUT Module 52 (34) DCBOPTCD 53 (35) Option Code DCBMAC DCBMACRF Overflow 56 (38) 54 (36) DCBNTM 55 (37) Index Size DCBCYLOF No. of Overflow Tracks DCBSYNAD Address of User's Synchronous Error Routine 62 (3E) 60 (3C) DCBRKP Relative Key Position DCBBLKSI Block Size Continued -Figure 40 3. Data Control Block - ISAM (Part 1 of 4) as System Control Blocks ( DATA CONTROL BLOCK -- ISAM Continued 64 (40) DCBMSWA Address of Work Area 70 (46) 68 (44) DCBSMSW Size of Work Area DCBSMSI Size of Area for Highest Level Index 72 (48) DCBNCP No. of Channel Programs 73 (49) DCBMSHI Address of Area for Highest Level Index 76 (4C) DCBSETL Address of SETL Module 80 (50) DCBEXCD1 81 (51) Condition Flags DCBEXCD2 82 (52) Condition Flags DCBLRECL Logical Record Length 84 (54) DCBESETL Address of ESETL Routine 88 (58) Address of READ K or DCBLRAN WRITE K or Read Exclusive Module 92 (5C) DCBLWKN Address of WRITE KN Module 96 (60) DCBRELSE Work Area for Register Contents 100 (64) DCBPUTX Work Area for Register Contents 104 (68) DCBRELX Address of Read Exclusive Module 108 (6C) DCBFREED Address of Dynamic Buffering Module 112 (70) DCBDBUFN Reserved 113 (71) DCBFTMI2 Direct-Access Address of Second-Level Master Index 120 (78) DCBLEMI2 Direct-Access Address of Last Entry in Second-Level Master Index 125 (7D) DCBFTMI3 Direct-Access Address of Third-Level Master Index 128 (80) Continued Figure 3. Data Control Block - ISAM (Part 2 of 4) » DCB -- ISAM 41 DATA CONTROL BLOCK -- ISAM Continued 132 (84) DCBLEMI3 Direct-Access Address of Last Entry in Third-Level Master Index 137 (89) DCBNLEV No. of Index Level s 141 (8D) DCBHMASK 2301, not 2301 Continued 144 (90) DCBHIRCM Highest R for Indexes 148 (94) 145 (91) DCBHIRPD Highest R for Prime Data DCBTDC Tag Deletion Count 152 (98) 138 (8A) DCBFIRSH HHR of First Prime Data Record 142 (8E) DCBLDT HH of Last Prime Data Track 146 (92) DCBHIROV Highest R for Overflow 150 (96) 147 (93) DCBHIRSH Last R of Shared Track DCBNCRHI Bytes Needed for Highest-Level Index DCBRDRG3 Count of Access to Overflow Records Other than the First 156 (9C) DCBNREC No. of Logical Records in Prime Data Area 160 (AO) DCBST 161 (A1) Status Indicators DCBFTCI Direct-Access Address of First Track of Cylinder Index 168 (A8) 169 (A9) Reserved DCBFTMl1 Direct-Access Address of First Track of 176 (BO) DCBNTHI Size of Highest Index First-L~vel Master Index 177 (B1) DCBFTHI Direct-Access Address of First Track of Highest-Level Index 184 (B8) DCBLPDA Direct-Access Address of Last Prime Data Record in Prime Data Area Figure 3,. Data Control Block - ISAM (Part 3 of 4) Continued ( 42 OS System Control Blocks DATA CONTROL BLOCK -- ISAM Continued 192 (CO) DCBLETI Direct-Access Address of Last Active Normal Entry of Track Index on Last Cylinder 198 (C6) 197 (C5) DCBNBOV No. of Bytes Left on Overflow Track Reserved 200 (C8) DCBLECI Direct-Access Address of Last Active Entry in Cylinder Index 205 (CD) 206 (CE) DCBRORG2 No. of Tracks Left in Overflow Area Reserved 208 (DO) DCBLEM'I1' Direct-Access Address of Last Active Entry in First-Level Master Index 213 (D5) 214 (D6) DCBNOREC No. of Logical Records in Overflow Area Reserved 216 (D8) DCBLlOV Direct-Access Address of Last Record in Overflow Area 224 (EO) DCBRORG1 No. of Full Cylinder Overflow Areas 226 (E2) Reserved 228 (E4) DCBWKPTl Pointer to Work Area or Channel Program 232 (E8) DCBWKPT2 Pointer to Work Area or Channel Program 236 (EC) DCBWKPT3 Pointer to Work Area or Channel Program 240 (FO) DCBWKPT4 Pointer to Work Area or Channel Program 244 (F4) DCBWKPT5 Pointer to Work Area or Channel Program 248 (F8) DCBWKPT6 Pointer to Work Area or Channel Program 251 (FB) Figure 3. Data Control Block - ISAM Disk Drive. Parallel Drum. Serial Drum. Disk Storage • Data Cell Drive • Disk Storage Facility. 2311 2301 2303 2302 2321 2314 Track balance. Number of bytes remaining on current track. COMMON INTERFACE 20 (14) 1 DCBBUFNO Number of buffers required for this data set: 21 (15) • 3 DCBBUFCB Address of buffer pool control block. 24 (18) 2 DCBBUFL Length of buffer: 26 (lA) DCBDSORG Before OPEN: Data set organization to be used. After OPEN: Data set organization in use. Byte 1 26 (lA) 0 • ••• x xx •• •• 1. ... 1 32,767. Code IS PS DA 1. . 1 .. . . 1. 0 - 0-255. PO U Indexed sequential organization. Physical sequential organization • Direct organization • (Reserved bits> Partitioned organization • Unmovable - the data contains location dependent information. Byte 2 27 (lB> 28 (lC> 1 ... .xxx xxxx 4 GS Graphics Organization. (Reserved bits) Reserved ( 44 OS System Control Blocks Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning FOUNDATION EXTENSION 32 (20) 1 DCBHIARC, DCBBFTEK, DCBBFALN x •• '. • x •• 0 •••• 0 •• 0 •••• 1 •• 1 •••. 0 •• Buffer pool location, coded in the DCB macro instruction: Before Open none No choice made in the DCB macro instruction. After Open If no choice is made in the DD statement either (as shown by the JFCBHIAR field), the Open routine resets these two bits from 00 to 01. o Hierarchy 0 main storage. (See also: After Open, above.) 1 Hierarchy 1 main storage,. (Reserved bits) .xxx x ••• • .xx • .10 • .01 D F • .,11 F Buffer alignment: Doubleword boundary. FUllword not a doubleword boundary, coded in the DCB macro instruction. FUllword not a doubleword boundary, coded in the DD statement. 33 (21) • 3 DCBEODAD Address of a user-provided routine to handle end-ofdata conditions. 36 (24) 1 DCBRECFM Record Format. Code 10 •• 01 •• 11.. F V U T B •• 1. •. .1 1 ..• S • 10. ,.01. M • 00. • .. 1 37 (25) • 3 DCBEXLST A Fixed length records. Variable length records. Undefined length records. Track overflow • Blocked records • may not occur with undefined (U). Standard records. No truncated blocks or unfilled tracks are embedded in the data set. ASA control character • Machine control character. No control character • Key length (KEYLEN) was specified in the DCB macro instruction; this bit is inspected by the open routine to prevent overriding a specification of KEYLEN=O by a non-zero specification in the JFCB or data set label. Exit List. Address of a user-provided list. » DCB -- ISAM 45 Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM This 8 byte name must be the same as that appearing in the name field of the data definition statement which defines the data set associated with this DCB. It is used by the open routine to locate the JFCB. 48 (30) 1 DCBOFLGS Flags used by the Open routine. 1 ••• o•• '. • 1,•• •• 1. •• • 1 1 ••• . 1 .. •• 0. '•• 1. •.• 1 49 (31) • 1 DCBIFLG 00 •• 01 •• 110. • • 10 •• 01 00 •• 11 •• 01 •• 10 •• •• xx Last I/O operation was a WRITE. Last I/O operation was a READ or POINT. For direct access devices, this means that the track balance field is invalid. Last I/O operation was in READ backward mode • Set to 1. by EOV routine when it calls the Close routine for concatenation of data sets with unlike attributes. An OPEN has been successfully completed • Set to 1. by a problem program to indicate a concatenation of unlike attributes. Tape mark has been read • Set to Q by an I/O support function when that function takes a user exit. It is set to Q to inhibit other I/O support functions from processing this particular DCB. Set to 1 on return from the user exit to the I/O support-function which took the exit. Set to 1. by an I/O support function if the DCB is to be processed by that function. Used by I/O supervisor in communicating error conditions and in determining corrective procedures. Not in error procedure. Error correction in process. Permanent error condition. Channel 9 printer carriage tape punch sensed • Channel 12 printer carriage tape punch sensed. Always use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. (Reserved bits) ( 46 OS System Control Blocks Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning FOUNDATION SEGMENT -- BEFORE OPEN (Continued) 50 (32) 50 (32) •• 2 DCBMACR Byte 1 00.0 0 ••• • .• x BISAM - Input Always zero for BISAM. READ Dynamic buffering • CHECK (Reserved bit) Byte 2 00.0 0000 •• 1. BISAM - output Always zero for BISAM. WRITE •. 1. • 1 •• · . 1. 51 50 Macro instruction reference: specifies the major macro instructions and various options associated with them. Used by the Open routine to determine access method. Used by the access method executors in conjunction with other parameters to determine which load modules are required. (33) R S C w Byte 1 0.0 • • 0 •• (32) • 1 •• ••.1 1 ••• • .. xx G M L Byte 2 51 (33) 1 ••• .1 •. S P •• 0. ••• 1 1 .... • 1 •• •• 1. •.. 1 M L U K I QISAM - Input Always zero for QISAM • GET Move mode of GET • Locate mode for GET. (Reserved bits) QISAM - output SETL PUT or PUTX. Always zero for QISAM • Move mode of PUT • Loca te mode of PUT .• Update in place (PUTX) • SETL by key • SETL by ID • FOUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT A two byte field containing the offset from the TIOT origin to the TIOELNGB field in the TIOT entry for the DD statement associated with this DCB. 42 (2A) •• 2 DC BMACRF Contents and meaning are the same as those of the DCBMACR field in the foundation before Open. 44 (2C) 1 DCBIFLGS Contents and meanings are the same as those of the DCBIFLG field in the foundation before Open. 45 (2D) .. 3 DCBDEBAD Address of the associated DEB .• Note: The above fields overlay the DCBDDNAM field during OPEN and are restored to their original form at CLOSE. 48 (30) 1 DC BOFLGS Contents and meanings are the same as those of the DCBOFLGS field in the foundation before Open. ) DCB -- ISAM 47 Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning ACCESS METHOD INTERFACE -- ISAM 49 (31) • 3 DCBGET, DCBPUT Address of GET module or of PUT module. 52 (34) 1 DCBOPTCD 1 ..• .x.. • x .• •• 1. • . •1 1 .... • . 1. •.. 1 53 (35) • 1 DCBMAC xxxx ••• x 1 •.• . 1 .. • . 1. option codes: Code W Write Validity check. (Reserved bits) Master Indexes • M Independent overflow area • I Cylinder overflow areaa Y L Delete option • Reorganization criteria • R Extension of the DCBMACRF field for ISAM. Code (Reserved bits) U Update for read. U Update type of write • A Add type of write • 54 (36) '.. 1 DCBNTM Number of tracks that determine the development of a Master Index. Maximum permissible value: 99. 55 (37) ••• 1 DCBCYLOF Number of tracks to be reserved on each cylinder to hold records that overflow from other tracks on that cylinder. Maximum permissible value: 99. 56 (38) 4 DCBSYNAD Address of user's synchronous error routine to be entered when uncorrectable errors are detected in processing data records. 60 (3C) 2 DCBRKP Relative position of the first byte of the key within each logical record. Maximum permissible value: logical record length minus key length. 62 (3E) •• 2 DCBBLKSI Block size. 64 (40) 4 DCBMSWA Address of a main storage work area for use by the control program when new records are being added to an existing data set. 68 (44) 2 DCBSMSI Number of bytes in area reserved to hold the highest level index. 70 (46) '.. 2 DCBSMSW Number of bytes in work area used by control program when new records are being added to the data set. 72 (48) 1 DCBNCP Number of copies of the READ-WRITE (type K) channel programs that are to be established for this data control block ( 99 maximum). 73 (49) • 3 DCBMSHI Address of a main storage area to hold the highest level index. 76 (4C) 4 DCBSETL Address of SETL module. ( 48 OS System Control Blocks Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning ACCESS METHOD INTERFACE -- ISAM (Continued) I 80 (50) DCBEXCDl 1 1 ... . 1 •. · .1 .• ... 1 1 ... • 1 •• • • 1. .•. 1 81 (51) . DCBEXCD2 1 1 ••• . 1 •• · .1. • .• 1 xxxx » First byte in which exceptional conditions detected in processing data records are reported to the user. Lower key limit not found. Invalid device address for lower limit • Space not found. Invalid request • Uncorrectable input error. Uncorrectable output error • Unreachable block • Overflow record • Second byte in which exceptional conditions detected in processing data records are reported to the user. Sequence check. Duplicate record • DCB closed when error was detected. Overflow record. (Reserved bits) 82 (52) •• 2 DCBLRECL Logical record length for Fixed-length record formats. Variable-length record formats: Maximum logical record length or an actual logical record length changed dynamically by the user when creating the data set. 84 (54) 4 DCBESETL Address of the ESETL routine in the GET module. 88 (58) 4 DCBLRAN Address of READ-WRITE K module or exclusive module. 92 (5C) 4 DCBLWKN Address of WRITE KN module. 96 (60) 4 DCBRELSE Work area for temporary storage of register contents. 100 (64) 4 DCBPUTX Work area for temporary storage of register contents. 104 (68) 4 DCBRELX Address of read exclusive module. 108 (6C) 4 DCBFREED Address of dynamic buffering module. 112 (70) 1 DCBDBUFN Reserved 113 (71) • 7 DCBFTMI2 Direct access device address of the first track of the second level master index (in the form MBBCCHH). 120 (78) 5 DCBLEMI2 Direct access device address of the last active entry in the second level master index (in the form CCHHR). 125 (7D) . 7 DCBFTMI3 Direct access device address of the first track of the third level master index (in the form MBBCCHH) • 132 (84) 5 DCBLIMI3 Direct access device address of the last active entry in the third level master index (in the form CCHHR). 137 (89) • 1 DCBNLEV Number of levels of index. 138 (8A) •• 3 DCBFIRSH HHR of the first data record on each cylinder. • • DeB -- ISAM 49 Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning 141 (8D) • 1 DCBHMASK 142 (8E) •• 2 • DCBLOT HH is the last prime data track on each cylinder. 144 (90) 1 DCBHIRCM Highest possible R for tracks of the cylinder and master indices. 145 (91) • 1 DCBHIRPD Fixed-length record format: Highest possible R for prime data tracks. 146 (92) •• 1 DCBHIROV Fixed-length record format: Highest possible R for overflow data tracks. 147 (93) ••• 1 DCBHIRSH R of the last data record on a shared track, if applicable. 148 (94) 2 DCBTDC Tag deletion count. 150 (96) •• 2 DCBNCRHI Number of storage locations needed to hold the highest level index. 152 (98) 4 DCBRORG3 For each use of the data set, the number of READ or WRITE accesses to an overflow record which is not the first in a chain of such records. 156 (9C) 4 DCBNREC Number of logical records in the prime data area. 160 (AO) 1 DCBST Status indicators. • 1 ••. • 1 •• •• 1. ••• 1 x ••• • 1 •• • • 1. ••• 1 07 FF Device is a 2301 drum. Device is other than a 2301 drum. Single schedule mode. Key sequence checking is to be performed • Loading has completed. Set to 1 by the Close routine and to 0 by the first execution of the Put routine. The extension of the data set will begin on a new cylinder. Reserved First macro instruction not yet received • Last block full • Last track full • 161 (Al) • 7 168 (A8) 1 169 (A9) • 7 DCBFTMIl Direct access device address of the first track of the first level master index (in the form MBBCCHH). 176 (BO) 1 DCBNTHI Number of tracks of high-level index. 177 (Bl) • 7 DCBFTHI Direct access device address of the first track of the highest level index (in the form MBBCCHH). 184 (B8) 8 • DCBLPDA Direct access device address of the last prime data record in the prime data area (in the form MBBCCHHR). 192 (CO) 5 • DCBLETI Direct access debice address of the last active normal entry of the track index on the last active cylinder (in the form CCHHR). 197 (C5) • 1 50 DCBFTCI Direct access device address of the first track of the cylinder index (in the form MBBCCHH). Reserved OS System Control Blocks Reserved ( Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- ISAM Hex. Dig. Field Description, Contents, Meaning ACCESS METHOD INTERFACE - ISAM (Continued) 198 (C6) •• 2 • OCBNBOV Number of bytes left on the current track of the independent overflow area. 200 (C8) 5 • OCBLECI Direct access device address of the last active entry in the cylinder index (in the form CCHHR). 20S (CO) • 1 206 (CE).. 2 208 (00) S 213 (OS) • 1 214 (06) •• 2 0 DCBNOREC Number of logical records in an overflow area. 216 (D8) 8 0 DCBLIOV Direct access device address of the last record written in the independent overflow area (in the form MBBCCHHR) • 224 (EO) 2 • DCBRORG1 Number of cylinder overflow areas that are full. 226 (E2) •• 2 228 (E4) 4 OCBWKPT1 A pointer to a work area or to a constructed channel program for which space is obtained by GETMAIN macro instructions issued by Open executors. 232 (E8) 4 DC BWKPT2 Additional pointer as in OCBWKPT1. 236 (EC) 4 DCBWKPT3 Additional pointer as in DCBWKPT1. 240 (FO) 4 DCBWKPT4 Additional pointer as in DCBWKPT1. 244 (F4) 4 DCBWKPTS Additional pointer as in DCBWKPT1. 248 (F8) 4 DCBWKPT6 Additional pointer as in DCBWKPT1. Reserved • • DCBRORG2 Number of tracks (partially or wholly) remaining in the independent overflow area. OCBLEMl1 Direct access device address of the last active entry in the first level master index (in the form CCHHR). Reserved Reserved ) DCB -- ISAM Sl ( Data Control Block-BDAM The data control block for BDAM is given below. The common interface and foundation sections are the same for all DeBs. The direct access storage device and BDAM interface sections complete this format of the DCB. Figure 4 illustrates the format of the data control block used in BDAM. Descriptions of the fields follow the illustration. DCB -- BDAM 53 DATA CONTROL BLOCK -- BDAM Device Interface 17 (11) 16 (10) DCBKEYLE DCBREL No. of Tracks or Blocks Key Length 19 (13) Common Interface 21 (15) 20 (14) DCBBUFCB Address of Buffer Pool Control Block DCBBUFNO No. of Buffers Required 26 (IA) 24 (18) DCBDSORG Data Set Organization DCBBUFL Buffer Length 28 (IC) DCBIOBAD First lOB Address 31 (1F) Foundation Extension 32 (20) DCBHIARC, DCBBTFEK, DCBFALN 33 (21) 36 (24) 37 (25) Reserved DCBEXLST Exit List Address DCBRECFM Record Format 39 (27) Foundation '-----Sef-o-re--OPE-i,r--------------------------------------------------.---------------------.---_.-----------------------------------------------.---------------------------.. -----.... -.--.--.--. 40 (28) DCBDDNAM DD Statement Name 48 (30) DCBOFLGS 49 (31) DCBIFLG 50 (32) Type of lOS Flags Open Flags ( DCBMACR Instruction and Options I/o Macro 51 (33) After OPEN 42 (2A) 40 (28) DCBTlOT Offset to DD Entry in TlOT 44 (2C) DCBIFLGS 45 (2D) 105 Flags 48 (30) Type of DCBMACRF Instruction and Options I/o Macro DCBDEBAD Address of DEB DCBOFLGS Open Flags -Figure 4. Data Control Block - BDAM (Part 1 of 2) c 54 OS system Control Blocks DATA CONTROL BLOCK -- BDAM BDAM Interface 49 (31) 52 (34) DCBOPTCD DCBREAD, DCBWRITE Address of Read or Write Module 53 (35) DCBCHECK Address of Check Module Option Codes 56 (38) DCBSYNAD Address of SYNAD Routi ne 60 (3C) 62 (3E) Reserved DCBBLKSI Maximum Block Size 64 (40) DCBIOBSQ Address of First lOB on Unscheduled Queue 68 (44) DCBSQND Address of Lost lOB on Unscheduled Queue 72 (48) DCBIOBUQ Address of First lOB on Un posted Queue 76 (4C) DCBUQND Address of Last lOB on Unposted Queue 80 (50) 81 (51) DCBLlMCT No. of Tracks/No. of Relative Blocks to be Searched Reserved 84 (54) DCBXCNT 85 (55) DCBXARG Address of Read Exclusive List 88 (58) DCBDRDX Address of Read Exclusive Module 92 (5C) DCBDFOR Address of Format Module 96 (60) DCBDFBK Address of Feedback Module 100 (64) DCBDYNB Address of Dynamic Buffer Module Figure 4. Data control Block - BDAM (Part 2 of 2) ) DCB -- BDAM 55 DATA CONTROL BLOCK -- BDAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DEVICE INTERFACE 16 (10) 1 DCBKEYLE Key length. 17 (11) • 3 DCBREL Number of relative tracks or blocks in this data set. COMMON INTERFACE 20 (14) p DCBBUFNO Number of buffers required for this data set. May range from 0 to 255. 21 (15) • 3 DCBBUFCB Address of buffer pool control block. 24 (18) 2 DCBBUFL Length of buffer. 26 (lA) •• 2 DCBDSORG Data set organization being used. 26 (lA) Byte 1 • •. 1 27 (lB) 28 (lC) Code xx.x xxx. •• 1. Byte 2 4 DCBIOBAD May range from 0 to 32,767. DA U (Reserved bits) Direct organization • Unmovable - the data contains location dependent information. Reserved Address of the standard fields of the first lOB in the pool of lOBS. FOUNDATION EXTENSION 32 (20) 1 DCBHIARC, DCBBFTEK, DCBBFALN x. •. .x .. 0 •••• 0 •• o. .. .1 .. 1. .• .0 .. Buffer pool location, coded in the DCB macro instruction: Before Open none No choice made in the DCB macro instruction. After Open If no choice is made in the DD statement either (as shown by the JFCBHIAR field), the Open routine resets these two bits from 00 to 01. o Hierarchy 0 main storage. (See also: After Open, above.) 1 Hierarchy 1 main storage. .xxx x ••• (Reserved bits.) • .xx 33 (21) • .10 • .01 D • .11 F • 3 F Buffer alignment: Doubleword boundary. Fullword not a doubleword boundary, coded in the DCB macro instruction,. Fullword not a doubleword boundary, coded in the DD statement. Reserved ( 56 OS System Control Blocks DATA CONTROL BLOCK -- BDAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning FOUNDATION EXTENSION (Continued) 36 (24) 1 DCBRECFM Record Format. Code 10 •• 01 •• 11. '. • .• 1. ••• 0 000,. '••• 1 37 (25) • 3 DCBEXLST F V U T Fixed record length. Variable record length. Undefined record length. Track overflow,. Always zeros • Key length (KEYLEN) was specified in the DCB macro instruction,. This bit is inspected by the Open routine to prevent overriding a specification of KEYLEN=O by a nonzero specification in the JFCB or data set label. Exit list. Address of a user-provided exit list. FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM This name must be the same as that appearing in the name field of the data definition statement which defines the data set associated with this DCB. 48 (30) 1 DCBOFLGS Flags used by the Open routine. 1 .••• • x'.. .x •• • .0.. 0 •••• .•. 1 •• 0. •. 1. ... 1 49 (31) • 1 DCBIFLG 00 •• 01 •• 11 •• 0.00 00 •• 11 •• 10 •• 01 •• •• xx The data set is being opened for INOUT or OUTPUT. (Reserved bits) Always set to Q. An OPEN has been successfully completed • Set to Q by an I/O support function when that function takes a user exit. It is set to 0 to inhibit other I/O support functions from processing this particular DCB. Set to 1 on return from user exit to the I/O support-function which took the exit. Set to ! by an I/O support function if the DCB is to be processed by that function. Used by I/O Supervisor in communicating error conditions and in determining corrective procedures. Not in error procedure. Error correction in process. Permanent error condition,. Always zeros. Always use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. Never use I/O supervisor error routine. (Reserved bits) ) DCB -- BDAM 57 DATA CONTROL BLOCK -- BDAM Offset Bytes and Alignment Field Name Field Description.. Contents.. M'eaninq FOUNDATION SEGMENT -- BEFORE OPEN (Continued) 50 (32) '.. 2 DCBMACR Macro instru~tion reference. Major macro instructions and various options associated with them that will be used. Byte 1 50 (32) 00. '• • ,.1. •• • 1 1,••• ,.1 •• '•• 1,. '. '•• 1 R K I S x C Always zero for BDAM. READ Key segment with READ • ID argument with READ. System provides area for READ (dynamic buffering). Read exclusive. CHECK macro instruction. Byte 2 51 (33) 000 • • • 1,. 1 •• '. W K I '•• 1,. A '••• 1 .x.x Always zero for BDAM. WRITE Key segment with WRITE. ID argument with WRITE. (Reserved bits) Add type of WRITE. FUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT Offset from the TIOT origin to the TIOELNGH field in the TIOT entry for the DD statement associated with this DeB. 42 (2A) •• 2 DCBMACRF contents and meaning are the same as DCBMACR in the foundation before OPEN. 44 (2C) 1 DeBIFLGS Contents and meaning are the same as DCBIFLG in the foundation before OPEN. 45 (2D) • DCBDEBAD Address of the associated DEB. Note: The above fields overlay the DCBDDNM field during OPEN and are restored to their original form at CLOSE. 48 (30) 1 DCBOFLGS contents and meaning are the same as DCBOFLGS in the foundation before OPEN. 3 ( 58 OS system Control Blocks DATA CONTROL BLOCK -- BDAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning ACCESS METHOD INTERFACE -- BDAM 49 (31) • 3 DCBREAD, DCBWRITE Address of the READ/WRITE module. 52 (34) 1 DCBOPTCD 1 ••• • 1. '. •• 1. .• • • 1 1 .•• . 1 .. •• 1. .•. 1 Option Codes: Code W Write validity check. Track overflow • E Extended search • F Feedback • A Actual addressing,. Dynamic buffering • Read exclusive,• R Relative block addressing • 53 (35) • 3 DCBCHECK Address of the CHECK module, IGG019LI. 56 (38) 4 DCBSYNAD Address of SYNAD (synchronous error) routine. 60 (3C) 2 62 (3E) •• 2 DCBBLKSI Maximum block size. 64 (40) 4 DCBIOBSQ Address of first IOB on unscheduled queue for either; A WRITE-add request when another WRITE-add is in progress, or a READ-exclusive request when the READexclusive list is full. 68 (44) 4 DCBSQND Address of last IOB on unscheduled queue. 72 (48) 4 DCBIOBUQ Address of the first IOB on the unposted queue. This queue is for IOBs requesting a record already under READ exclusive control. 76 (4C) 4 DCBUQND Address of the last job on the unposted queue that is maintained by the READ exclusive module. 80 (50) 1 81 (51) '. 3 DCBLIMCT Number of tracks or number of relative blocks to be searched (extended search option). 84 (54) 1 OCB XC NT Number of entries in the READ exclusive list. 85 (55) '. 3 DCBXARG Address of the READ exclusive list. 88 (58) 4 DCBDRDX Address of the READ exclusive module. 92 (SC) 4 DCBDFOR Address of a FORMAT module. 96 (60) 4 DCBDFBK Address of a FEEDBACK module. 100 (64) 4 DCBOYNB Address of dynamic buffer module. Reserved Reserved ) DCB -- BDAM 59 ( Data Control Block-QTAM The format of a data control block (DeB) in QTAM is determined by the character of the data set and is shown by variations in the block segments. Figure 5 shows the format of the block by segments; descriptions of the fields follow the illustration. QTAM Data Sets QTAM message processing programs and QTAM message control programs use a data control block (DeB) to describe their respective data sets: • processing Program Message Queues. • Direct-Access Storage Device (DASD) Message Queues. • Line Groups. • Checkpoint Data Set. The checkpoint DeB is identical in format to that used for the DASD message queue; it is distinguished by the entry TPCHKPNT in the DCBDDNAM field in the foundation segment before Open. QTAM DCB Segments The three segments of a DCB, and their uses in QTAM, shown and described here, are: Prefix Segment • Line Group Interface. • Processing Program Message Queue Interface. • DASD Message Queue Interface, Checkpoint Data Set Interface. Foundation Segment • Before Open. • After Open. Extension Segment • Line Group Extension (Polling List Origin). • Processing Program Message Queue Extension. ) DeB -- QTAM 61 DATA CONTROL BLOCK -- QTAM WTTA Interface 16 (10) 17(11) DCBBQFLG WTTA Flags 18 (12) 19 (13) DCBWTEOM EOM Character DCBWTEOT EOT Character DCBWTPAD No. of Padding Characters Data Set Interface ---I.Tiie---Gro.u-p----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------1 21 (IS) 20 (14) DCBCLPS Address of the LPS Routine DCBBUFRQ Buffers Requested 24 (18) DCBINTVL Intentional Interval 25 (19) DCBACLOC 26 (1A) DCBDSORG Data Set Organization Offset , 28 (IC) DCBDEVTP 29 (lD) DCBIOBAD Address of First lOB Device Type 33 (21) 32 (20) DCBCPRI Priority DCBLCBAD Base for Addressing LCBs 37 (25) 36 (24) DCBEXLST Address of the Exit List DCBEIOBX Size of the LCB 38 (27) i Processing Program Message Queue 21 (15) 20 (14) DCBTRMAD Address of the Terminal Name DCBBUFRQ Buffers to be Filled 26 (IA) 24 (18) 28 (lC) DCBSEGAD Address of Current Segment 32 (20) DCBEODAD Address of the EODAD Routine 37 (25) 36 (24) DCBRECFM Record Format DASD Message DCBEXLST Address of the Exit List DCBBUFNO 21 (15) Reserved DCBBUFCB Address of Terminal Table 26 (lA) 24 (18) DCBBUFL Length of the Data 28 (lC) DCBIOBAD Address of the lOB 5. 39 (27) Queue I Checkpoint 20 (14) Figure DCBDSORG Data Set Organization DCBSOWA Size of the Work Area DCBDSORG Data Set Organization 31 (IF) Data Control Block - QTAM (Part 1 of 2) ( 62 OS System Control Blocks DATA CONTROL BLOCK -- QTAM j····.Seiiire··.OPffr.·.......··.·............·..···............................................................................................................................................. . Foundation 40 (28) DCBDDNAM DD Statement Data Set Name 48 (30) 50 (32) 49 (31) DCBOFLGS Open Routine Flags I/o DCBIFLGS Supervisor Flags DCBMACR Macro Instructi ons 51 (33) After OPEN 40 (28) 42 (2A) DCBTlOT Offset in TlOT Table to DD Entry 44 (2C) 45 (2D) I/o 48 (30) DCBMACRF Macro Instruction DCBIFLGS Supervisor Flags DCBOFLGS Open Routine Flags DCBDRBAD Address of the DEB 49 (31) .. .. --- .. --- .. --------- ..... ----- .. -... -- .... ----------- ... Extension ------~ , DCBREAD I DCBWRITE I DCBGET I DCBPUT Address of the Access Modules --------------------------------------------~ 51 (33) .. --- .... ----- ... .. -- .... - ........ _------_ ..... --------- .. - .... --_ .. ------ ............. - ..... - .. --_ .. - .................... --_ ........... ---_ ........ --........ -_: ·····Cfne-·Gj.·o·u·p···································.. --...... -... -... -.........-.. ------... ---..... ----------.... -------.. -.......... -.-..-..... -.-...... -... -.........--.. -... -.. -...... --...... -52 (34) DCBKSTAT Error Threshold 56 (38) DCBCPOLL Polling List Origin I DCBCPOLL l r-59 (3B) r-f-- DCBCPOLL I DCBCPOLL Processing Program Message Queue 52 (34) DCBRECRD Not Used 56 (38) DCBSYNAD Address of the SYNAD Routine l. . . . ~._.~. _.~_ _ . . . . . . . . . . . . . ._. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60 (3C) Figure DCBEOBLK Not Used 5. 63 (3F) Data Control Block - QTAM (Part 2 of 2) ) DCB -- QTAM 63 DATA CONTROL BLOCK -- QTAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning WTTA Interface 16 (10) OCBBQFLG 1 x •• '. .xxx • 1 •• ,. ,.1. '. '. ,.1 1 ••• ·1 17 (11) 18 (12) 1 19 (13) . 1 WTTA flag byte. (Reserved bits) WRU feature is to lAM feature is to WRU feature to be WRU feature is to be used • be used. used in the Send Header subgroup. be used in the End Send subgroup.. OCBWTEOM The EOM character. DC BWTEOT The EOT character. OCBWTPAD Number of padding characters required for motor-on delay,. LINE GROUP INTERFACE 20 (14) 1 DCBBUFRQ Number of buffers requested for a read or write operation. 21 (15) • 3 DCBCLPS Address of the line procedure specification routine .• 24 (18) 1 DCBlNTVL Number of seconds of intentional delay between passes through a polling list for nonswitched lines. 25 (19) • 1 DCBACLOC Offset, relative to zero, of the device access field for each terminal table entry. 26 (lA) '.. 2 DCBDSORG Data set organization. 26 (lA) Byte 1 xx •• xxxx CX •• 01 27 (lB) 28 (lC) 1 29 (10) • 32 (20) 1 Byte 2 3 Device type pointer. DCBlOBAD Address of first lOB. DCBCPRl Communication priority,. Relati ve priority to be given to sending and receiving operations. ,.1,•• • ,.1. • '•• 1 (21) · 36 (24) 37 (25) Reserved OCBOEVTP xxx x x·•• '. 33 (Reserved bits) Line group • R E S (Reserved bits) Receiving has priority. Receiving and sending have equal priority,• Sending has priority • DCBLCBAD Base for addressing LCBs. (Base = Address of first LeB -- length of one LCB). 1 DCBEIOBX Extended lOB index. (LCB) '. ·3 DCBEXLST Address of the exit list,. 3 Size of a line control block ( 64 OS System Control Blocks DATA CONTROL BLOCK -- QTAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning PROCESSING PROGRAM MESSAGE QUEUE INTERFACE 20 (14) 1 DCBBUFRQ Number of buffers to be filled from the direct access queue. 21 (15) • 3 DCBTRMAD Address of a user-provided area in which the terminal name is stored. 24 (18) 2 DCBSOWA Size of the user-provided work area. 26 (lA) •• 2 26 (lA) DCBDSORG Byte 1 xxxx x.xx Data set organization. Code (Reserved bits) MQ Problem program message queue • • 1 •• 27 (lB) 28 (lC) 4 DCBSEGAD Address of current segment. 32 (20) 4 DCBEODAD Address of a user-provided routine. 36 (24) 1 DCBRECFM Record Format. Code (Reserved bits) R Record G Message S Segment Byte 2 0000 ••• 0 '•.• 1. .1,•• 1 ••• 37 (25) • 3 DCBEXLST Reserved Address of the exit list. DIRECT ACCESS STORAGE DEVICE (DASD) MESSAGE QUEUE INTERFACE, CHECKPOINT DATA SET INTERFACE 20 (14) 1 DCBBUFNO Reserved 21 (15) • 3 DCBBUFCB Address of the terminal table. 24 (18) 2 DCBBUFL Size of the data in the buffer equated to IECKBUFL. 26 (lA) •• 2 26 (llA) 27 (lB) 28 (lC) 4 DCBDSORG Byte 1 xxxx .xxx 10 •• Data set organization. Code (Reserved bits) CQ Direct-access message queue Byte 2 Reserved DCBIOBAD Address of input/output block. FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM Data set name as used in data definition statement. Used by Open routine to locate address of job file control block (JFCB). Note: If the DD name is TPCHKPNT, this DCB is used for the checkpoint data set. ) DCB -- QTfu'vl 65 DATA CONTROL BLOCK -- QTAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning FOUNDATION SEGMENT 48 (30) 9 DCBOFLGS xxx. xxx. ,. ,. ,.1 • '•• 1 49 (31) • 1 DCBIFLGS 00. '. 01 •• 11 ... • .10 • .. 01 00 •• 11 •• 10 •• 01 •• •• xx 50 (32) 50 (32) •• 2 DCBMACR Byte 1 x,•• x xxxx . 1 •• • .1,. 51 Byte 2 x,•• x xxxx (33) ,.1,. '. • .1,. BEFORE OPEN (Continued) Flags used by OPEN. (Reserved bits) Opening has been successfully completed. This bit is set to 1 by an I/O support routine if the DCB is to be processed by that routine. Used by lOS in communicating error conditions and in determining error procedures. Not in error procedure. Error correction in process. Permanent error conditi 00.. Channel 9 printer carriage punch. Channel 12 printer carriage punch. Always use lOS error routine. Never use lOS error routine. Never use lOS error routine. Never use lOS error routine. (Reserved bits) Macro instruction reference -- specifies the major macro instructions and various options associated with them. Used by open routine to determine the access method. (Reserved bits) PUT for message queue • WRITE for line group. (Reserved bits> GET for message queue. READ for line group. FOUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT Points to the DO entry in the task I/O table for this DCB. It is the offset of the DO entry from the beginning of the task I/O table. 42 (2A) •• 2 DCBMACRF Contents and meaning are the same as DCBMACR in the foundation before execution of open. 44 (2C) 1 DCBIFLGS Contents and meaning are the same as DCBIFLGS in the foundation before execution of open. 45 (2D) • DCBDEBAD Address of the DEB associated with this DCB. 48 (30) 1 DCBOFLGS contents and meaning are the same as DCBOFLGS in the foundation before execution of open,. 49 (31) • 3 DCBREAD, DCBGET, DCBPUT, DCBWRITE Address of the READ, GET, PUT, and WRITE module. 3 ( 66 OS System Control Blocks DATA CONTROL BLOCK -- QTAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning LINE GROUP EXTENSION (POLLING LIST ORIGIN) 52 (34) 4 52 (34) Byte 1 Threshold value for number of transmissions. 53 (35) Byte 2 Threshold value for number of data checks. 54 (36) Byte 3 Threshold value for number of interventions required. 55 (37) Byte 4 Threshold value for number of timeouts. 56 (38) 56 (-38) n times DCBKSTAT DCBCPOLL Byte 1 xxxx ,.xxx i .... 57 (39) Byte 2-4 Four threshold values for error counts. A 4-byte fie1d for each (n) po11ing 1ist. Adapter type (Reserved bits) WTTA Address of the po1ling 1ist. PROCESSING PROGRAM MESSAGE QUEUE EXTENSION 52 (34) 4 DCBRECRD Not used by QTAM. 56 (38) 4 DCBSYNAD Address of the user provided routine to be entered if a work unit is 10nger than the work area provided for input. 60 (3C) 4 DCBEOBLK Not used by QTAM .• ) DCB -- QTAM 67 ( Data Control Block-BTAM The data control block (DeB> used in BTAM is described in the following. The common interface and foundation extension exist for all DeBs. Figure 6 illustrates the format of this DeB; a description of the fields follows the illustration. ) DeB -- BTAM 69 DATA CONTROL BLOCK -- BTAM WTTA Interface 16 (10) 17 (11) DCBBQFLG WTTA Flags 18 (12) DCBWTEOM EOM Character 19 (13) DCBWTPAD Number of Padding Characters DCBWTEOT EOT Character Common Interface 20 (14) DCBBUFNO Number of Buffers 24 (18) 28 (Ie) DCBBUFCB Address of Buffer Pool Control Block 21 (15) DCBBUFL Buffer Length DCBDEVTP Index to Directory I/O Directory DCBDSORG Data Set Organization 26 (I A) 29 (ID) DCBIOBAD Base for Addressing lOBs Foundation Extension 32 (20) DCBHIARC, DCBBFTEK 36 (24) 33 (21) DCBERROP Error Recovery Procedures 37 (25) DCBEIOBX Size of lOB 34 (22) Reserved DCBEXLST Address of User-Provided List r-.Foundation . . . . . ·. -..-.. . . -----.. . . . ·---.. .-----·---.. -.. . ---..-.. . -.. . . . .--.. .----------------.. . ----.. --.. . . . --.. . . . . . . . . . --.. -.--.. . . .-.. . --.. --.. . . . -.. -.. . . . . . . . -.. -.. . . --------.. ---.. . . -.. ----.. . -.. . -----.. . . . . . -.. . . . . . ----.. . ----.. . . . . . . . : ~ ! i:::)dation i! iI ! Before OPEN Jl i DCBDDNAM Name From DD Statement ~- 48 (30) DCBOFLGS Open Flags 49 (31) DCBIFLG lOS Error Flags "'1-' DCBMACR Type of I/O Macro Instruction and Options 50 (32) I , Foundation After OPEN 40 (28) DCBTlOT Offset to DD Entry in TIOT 44 (2C) DCBIFLGS lOS Error Flags 48 (30) DCBOFLGS Open Flags : !: 45 (2D) DCBMACRF Type of I/O Macro Instruction and Options 42 (2A) 1 ! DCBDEBAD Address of DEB S-TA-,Vi--inte-rfcice---------------------------------------------------------------------------------------------------------------------------------------------------------------------------, r- 49 (31) 148 (30) DCBLERB Address of Line Error Block 52 (34) -Figure DCBREAD, DCBWRITE Address of Read or Write Module 6. Data Control Block - BTAM (Part 1 of 2) ( 70 OS System Control Blocks DATA CONTROL BLOCK -- BTAM sse Interface - Before Open 57 (39) 56 (38) Reserved 58 (3A) Reserved DCBBSTSX Address of the Interface Resolution Routine 60 (3C) - DCBXCODE PTOP Flag 64 (40 ) -i..- Tsse Interface - After Open 56 (38) DCBXMODE BSC Transmission Mode 57 (39) 60 (3C) DCBBSTSX DLE 61 (3D) Reserved 99 (63)T DCBXCODE Control Station Flag Transmission Code DCBBSSTX STX DCBBSAKO ACK-O 64 (40) 68 (44) DCBBSENQ ENQ 72 (48) DCBBSEOT EaT 69 (45) 58 (3A) DCBBSRSV DLF 59 (3B) DCBBSWBT WBT 62 (3E) DCBBSTEX DLE 63 (3F) DCBBSETX ETX DCBBSAKI ACK-l 66 (42) DCBBSNAK NAK 70 (46) 73 (49) DCBBSETB ETB 71 (47) DCBBSDLE DLE DCBBSSYN SYN, SYN, SYN 76 (4C) DCBBSONL 78 (4E) 80 (50) DCBBSRVI 82 (52) DCBBSSAK -'- ~ Reserved T -Figure 6. Data Control Block - BTAM (Part 2 of 2) ) DCB -- BTAM 71 DATA CONTROL BLOCK -- BTAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning WTTA Interface 16 (10) 17 (11) 18 (12) 19 (13) 1 • 1 1 1 DCBBQFLG WTTA flag byte. x •• x xxxx . 1 •• .. 1. (Reserved bits.) WRU feature to be used • lAM feature to be used,• DCBWTEOM The EOM character. DCBWTEOT The EOT character. DCBWTPAD Number of padding characters required for motor-on delay. COMMON INTERFACE 20 (14) 1 DCBBUFNO Number of buffers obtained by the Open routine. Range: 0-255 21 (15) • 3 DCBBUFCB Address of the buffer pool control block. 24 (18) 2 DCBBUFL Buffer length,. 26 (lA) •• DCBDSORG Data set organization being used: 26 (lA) 2 Byte 1 xxx. xxxx CX • • ,.1 27 (lB) 28 (lC) 29 (lD) Range: 0 - 32,760 bytes (Reserved bits) Telecommunications -- line group • Byte 2 Reserved 1 DCBDEVTP Index to the device entry in the device I/O directory. • 3 DCBIOBAD Base for addressing lOBs. (Base = Address of first lOB -- length of an lOB) FOUNDATION EXTENSION 32 (20) 1 DCBHIARC, DCBBFTEK Code x. •• • x •• o•• '. .0 •• o. .. .1 .. 1 ••• ,.0 •• .xxx •• xx x ••• 1 ••• Buffer pool location, coded in the DCB macro instruction: Before Open none No choice made in the DCB macro instruction. After Open If no choice is made in the DD statement either (as shown by the JFCBHIAR field), the Open routine resets these two bits from 00 to 01. o Hierarchy 0 main storage. (See also: After Open, above.) 1 Hierarchy 1 main storage. (Reserved bits.) Buffering Technique: D Dynamic buffering. ( 72 OS System Control Blocks DATA CONTROL BLOCK -- BTAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning FOUNDATION EXTENSION (Continued} 33 (21) • 1 DCBERROP xxx. ••• 1 1 ••. . 1 .. •• 1. ••• 0 ..• 1 Error recovery procedure: Code (Reserved bits) T On-line test facilities to be used • Threshold and cumulative error counts to be C maintained. W Text-write errors to be retried • R Text-read errors to be retried • E Basic error procedures to be followed • N No error recovery procedures to be followed • (22) • 35 (23) ••• 1 36 (24) 1 DCBEIOBX Size of extended lOB. Size of an lOB associated with this DCB. 37 (25) • 3 DCBEXLST Address of (a user-provided) exit list. • 1 DCBBUFCT Contains maximum number of buffers to be obtained by BTAM for a Read or write operation (dynamic buffering only). Reserved FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM DD name of the data set. This name is matched to the name field of the data definition (DD) statement. (It is used by the Open routine to locate the appropriate DD entry in the task input/output table (TIOT).) 48 (30) 1 DCBOFLGS Flags used by the Open routine: xxx. xx.x (Reserved bits) OPEN has been successfully completed • Set to Q by an I/O support function when that function takes a user exit. (It is set to 0 to inhibit other I/O support functions from processing this particular DCB.) Set to 1 on return from the user exit to the I/O support function which took the exit. •• • 1 •• 0. • • •• • .1. 49 (31) • 1 DCBIFLG Flags used by I/O supervisor to communicate error conditions and to determine corrective procedures: 00 •• 01 •• 11 •• • • 10 •• 01 Not in error procedure. Error correction in process. Permanent error condition. Channel 9 printer carriage tape punch sensed • Channel 12 printer carriage tape punch sensed • Always use I/O supervisor error routine. Test lOS mask (IMSK) for error procedure. Never use I/O supervisor error routine. (OPEN sets these bits.) (Reserved bits) 00 •• 01 •• 11 •• 10 •• 01 •• •• xx ) DCB -- BTAM 73 DATA CONTROL BLOCK -- BTAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning FOUNDATION SEGMENT -- BEFORE OPEN (Continued) 50 (32) 50 (32) '.. 2 DCBMACR Macro instruction reference: Byte 1 xx.x xxxx •• 1. (Reserved bits) READ Byte 2 51 xx.x xxxx (33) ,•. 1. (Reserved bits) WRITE FOUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT Offset of the TIOELNGH field to the TIOT reference point. The TIOELNGH field is located in the DD entry of the TIOT that was created from the DD statement associated with this DCB. 42 (2A) •• 2 DCBMACRF Contents and meaning are the same as in DCBMACR field before Open. 44 (2C) 1 DCBIFLGS contents and meaning are the same as in DCBIFLG field before Open. 45 (2D) • DCBDEBAD Address of the associated DEB 3 Note: The above fields overlay the DCBDDNAM field during OPEN and are restored to their original form at CLOSE. 48 (30) 1 DCBOFLGS Contents and meaning are the same as in DCBOFLGS field before OPEN. ACCESS METHOD INTERFACE -- BTAN 49 (31) • 3 DCBREAD, DCBWRITE Address of READ/WRITE routine. 52 (34) 4 DCBLERB Address of line error block. BSC Interface -- Before Open 56 (38) 1 57 (39) • 1 Reserved DCBXCODE PTOP flag. x.xx xxxx (Reserved bits) If PTOP is specified in the SYSGEN procedure: Schedule an asynchronous exit to the interface resolution routine. .1. '. 58 (3A) •• 2 60 (3C) 4 64 (40) 36 Reserved DCBBSTSX If PTOP is specified in the SYSGEN procedure: Address of the interface resolution routine. Reserved ( 74 OS System control Blocks DATA CONTROL BLOCK -- BTAM Offset Bytes and Field Alignment Name Field Description, Contents, Meaning BSC Interface -- After Open 56 (38) 1 DCBXMODE Mode of transmission for binary synchronous communication (BSC). • 1 •• • ,.1. x •• x .xxx Intermediate block checking is to be performed • Transmission is through a 2701 Data Adapter Unit Dual Communication Interface B. Transmission is in code B for a 2701 Data Adapter Unit Dual Code Feature. Reserved DCBXCODE BSC control station flag# transmission code. x •• '. BSC control station flag. This is the control station a This is the remote station. 1 .•• 57 (39) 1 0,••• 1,•• '. » • x •• .1,•• If PTOP is specified in the SYSGEN procedure: Schedule an asynchronous exit to the interface resolution routine. ,•• 1.1 ••• • .,.1 .1 •• 00 •• 6-bit Transcode is being used. USASCII transmission code is being used. EBCDIC transmission code is being used. •• xx (Reserved bits) 58 (3A) 1 DCBBSRSV DLE control character. 59 (3B) 1 DCBBSWBT WBT control character. 60 (3C) 1 DCBBSTSX DLE control character. 61 (3D) 1 DCBBSSTX STX control character. 62 (3E) 1 DCBBSTEX DLE control character. 63 (3F) 1 DCBBSETX ETX control character. 64 (40) 2 DCBBSAKO ACK-O control character. 66 (42) 2 DCBBSAKl ACK-l control character. 68 (44) 1 DCBBSENQ ENQ control character. 69 (45) 1 DCBBSNAK NAK control character. 70 (46) 1 DCBBSETB ETB control character. 71 (47) 1 DCBBSDLE DLE control character. 72 (48) 1 DCBBSEOT EOT control character.. 73 (49) 3 DCBBSSYN SYN# SYN, SYN control characters. 76 (4C) 2 DCBBSONL SOH % control characters. 78 (4E) 2 DCBBSSAK DLE SAK control characters. 80 (50) 2 DCBBSRVI DLE 82 (52) 18 ~ control characters. Reserved DCB -- BTAM 75 ( Data Control Block-GAM This data control block (DeB) is used by the graphics access method (GAM) routines. It has the common interface and foundation sections. which serve the same purposes for all access method routines, although the format may vary slightly among them. An interface section that contains information about a particular graphic device precedes the common section. Figure 7 illustrates the format of the DeB used in GAM. Descriptions of the fields follow the illustration. ) DeB -- GAM 77 DATA CONTROL BLOCK -- GAM Graphic Device Interface teo) ~I"" 1 -r-- Reserved 12 (C) 14 (E) DCBBRSA Buffer Restart Address 16 (10) 15 (F) DCBGTYPE Basic/Express Reserved 18 (12) DCBBFRST Buffer Start Address DCBBFRSZ Buffer Size 19 (13) Common Interface 20 (14) Reserved 26 (IA) 28 (1C) DCBDSORG Data Set Organization DCBIOBAD Address of First lOB 31 (1 F) Foundation Extension 32 (20) 33 (21) 36 (24) 37 (25) DCBGNCP No. of I/o Instructions Before WAIT DCBPOLST Address of DCB List for Polling DCBEXLST Address of User's Exit List Reserved Foundation r---B.for.--Optf.j----------------------------------------------------------------------.-------------~--------------------------- 39 (27) . --------~-~---.----.--.----.-------------'1 40 (28) DCBDDNAM Name from DD Statement 48 (30) DCBOFLG 49 (31) DCBIFLG 50 (32) 105 Error Flags Open Flags DCBMACR Type of Macro Instruction and Options 51 (33) After OPEN 40 (28) 44 (2C) DCBTIOT Offset to DD Entry in T/OT DCBIFLGS 105 Error Flags 48 (30) DCBOFLGS 45 (2D) .,.. 49 (31) Open Flags Figure 7. 42 (2A) DCBMACRF Type of I/O Macro Instruction ond Options DCBDEBAD Address of DEB DCBGIOCR Address of I/o Control Routine 51 (33) Data Control Block - GAM ( 78 OS System Control Blocks Offset Bytes and Alignment Field Name DATA CONTROL BLOCK -- GAM Hex. Dig. Field Description, Contents, Meaning DEVICE-DEPENDENT INTERFACE o (0) 12 12 (c) 2 14 (E) •• Reserved Blank before execution of the second I/O operation. Last buffer start address. DCBBRSA DCBGTYPE 1 00 01 Type of buffer management and attention handling. Express Basic Reserved 15 (F) 16 (10) 2 DCBBFRST Blank before execution of Open routine. starting address for the buffer after execution of Open routine. 18 (12) •• 2 DCBBFRSZ Blank before execution of Open routine. Size of buffer after execution of Open routine. ••• 1 COMMON INTERFACE 20 (14) 6 26 (lA) •• 2 26 (lA) 27 (lB) Reserved DCBDSORG Byte 1 All zeros. Byte 2 Code GS Graphics organization. (Reserved bits) 1 •.• .xxx xxxx 28 (lC) 4 Data set organization. DCBIOBAD Blank before execution of Open routine. Address of the standard fields of the first input/ output block (lOB) after execution of Open routine. FOUNDATION EXTENSION 32 (20) 1 DCBGNCP Number of I/O instructions to be issued before a WAIT macro instruction. 33 (21) • 3 DCBPOLST Address of area where a DCB list is to be constructed for polling purposes. 36 (24) 1 37 (25) • 3 Reserved DCBEXLST Address of user's exit list. FOUNDATION SEGMENT FOUNDATION SEGMENT -- BEFORE OPEN 40 (28) 8 DCBDDNAM Eight byte name from the data definition statement that defines the data set associated with this DCB. ) DCB -- GAM 79 Offset 48 (30) Bytes and Alignment 1 Field Name DCBOFLG 1. '. ,. 0,•• '. .x •• • ,.1,. • '. ,.1 1. '.• • 1 •• . '. o. '•• 1. •.. 1 DATA CONTROL BLOCK -- GAM Hex. Dig. Field Description, Contents, Meaning Flags used by the Open routine. Last I/O operation was a GWRITE. Last I/O operation was a GREAD. (Reserved bit) set to ! by EOV when it calls the Close routine for concatenation of data sets with unlike attributes. An OPEN has been successfully completed. Set to ! by a problem program to indicate a concatenation of unlike attributes. Tape mark has been read • set to Q by an I/O support function when that function takes a user exit. It is set to Q to inhibit other I/O support functions from processing this particular DCB. set to 1 on return from the user exit to the I/O support-function which took the exit. set to ! by an I/O support function if the DCB is to be processed by that function. 49 (31) • 1 DCBIFLG set to zero by the graphics routines but used by I/O supervisor in communicating error conditions and in determining corrective procedures. 50 (32) •• 2 DCBMACR Major macro instructions and their associated options. 50 (32) xx.x xx.x Byte 1 • .1,. '•• 1. 51 xx.x xx.x (33) Byte 2 • .1,. •• 1. (Reserved bits) Read operation to be performed. Control operation to be performed with the read operation. (Reserved bits) Control operation to be performed with the write operation. • FOUNDATION SEGMENT -- AFTER OPEN 40 (28) 2 DCBTIOT Offset from the TIOT origin to the DD entry associated with this DCB. 42 (2A) '.. 2 DCBMACRF Contents and meaning are the same as DCBMACR field in the foundation segment before OPEN. 44 (2C) 1 DCBIFLGS Contents and meaning are the same as DCBIFLG field in the foundation segment before OPEN. 45 (2D) • 3 DCBDEBAD Address of the associated DEB. Note: The above fields are overlayed on the DCBDDNAM field during OPEN and are restored to their original form at CLOSE. 48 (30) 1 DCBOFLGS contents and meaning are the same as DCBOFLG field in the foundation segment before OPEN,. 49 (31) • 3 DCBGIOCR Address of the graphics input/output control routine. ( 80 OS system control, Blocks Data Extent Blocks There are two kinds of data extent blocks -- an ordinary one, used in all access methods (including BTAM and the message control portion of QTAM). and another one used in the message processing portion of QTAM. Accordingly, separate diagrams and descriptions are presented for the following uses of DEBs: • Ordinary • QTAM Message Processing Program » DEB 81 ( Data Extent Block-Ordinary The data extent block (DEB) contains an extension of information in the DCB. Each DEB is associated with a DCB, and the two point to each other. The DEB contains information concerning the physical characteristics of the data set and other information that is used by the control program. Figure 8 illustrates the format of the DEB. Descriptions of the fields follow the illustrations. This data extent block is used in all access methods and is used in QTAM by a message control program to describe a queue which is on a direct access storage device or to describe a line group. (QTAM processing programs use a DEB described separately.) DEB 83 DATA EXTENT BLOCK -- ORDINARY Appendage Table -36 (-24) DEBEOEA (I) Address of End-of-Extent Appendage -32 (-20) DEBSIOA (I) Address of Start I/o Appendage -28 (-IC) DEBPCIA(I) Address of PCI Appendage -24 (-18) DEBCEA (I) Address of Channel-End Appendage -14 (-20) DEBXCEA (I) Address of Abnormal-End Appendage -17(-11) DEB Prefix -16 (-10) DEBWKARA I/o Support Work Area -15 (-F) DEBDSCBA Address of DSCB -8 (-8) DEBDCBMK DCB Modification Mask -4 (-4) DEBLNGTH Length of DEB -3 (-3) Reserved -1 (-1) Basic Section 0(0) DEBNMSUB No. of Subroutines 1 (1) DEBTCBAD Address of TCB 4 (4) DEBAMLNG Acc M S'n Length 5 (5) DEBDEBAD Address of Next DEB 8 (8) DEBOFLGS Data Set Status 9 (9) DEBIRBAD Address of IRB 12 (C) DEBOPATB Type of I/O 13 (D) 16 (10) DEBNMEXT No. of Extents 17 (11) DEBUSRPG Address of First lOB in User Purge Chain 20 (14) DEBPRIOR Priority 21 (15) DEBECBAD Address of Parameter List to Find Purge ECB 24 (18) DEBPROTG, DEBDEBID Protection Key, DEB Id 25 (19) 28 (lC) 29 (lD) DEBEXSCL Extent Scale DEBQSCNT PURGE - Quiesce Count 14 (E) Reserved DEBDCBAD Address of DCB DEBAPPAD Address of I/o Appendage Vector Table 31 (IF) (I) Field names used only in BTAM and parts of QTAM. Figure 8. Data Extent Block -- Ordinary (Part 1 of 4) ( 84 OS System Control Blocks DATA EXTENT BLOCK -- ORDINARY 32 (20) DEBNIEE No. of Extents 33 (21) DEBFIEAD Address of Fi rst Index Extent 36 ('24) DEBNPEE No. of Extents 37 (25) DEBFPEAD Address of First Prime Data Area Extent 40 (28) DEBNOEE No. of Extents 41 (29) DEBFOEAD Address of First Overflow Extent 44 (2C) DEBDISAD Address of Privileged Module 47 (2F) 5e-,,-ice--oep-e-n(j-en-f--se-ct"i"on-----------------------------------------------------------------------------"----------------------------------------------------____________________ J ---[jnlf-R-e-cord-~-M-ag-rietic--ta-pe--Ijev-fces--se-c"ffon------- --------------------------------------------------------------------------------------------------r 32 (20) DEBDVMOD Device Modifier 32 (20) DEBUCBAD Address of UCB 33 (21) DEBUCBAD Address of UCB Reserved I 35 (23) I- 35 (23) I-i-- I DIrect I - Access DEBDVMOD File Mask +0 St ora< e DeVlce DEBUCBAD Sec t'Ion DEBUCBAD Address of UCB +1 II-- +4 DEBBINUM Bin Number +6 DEBSTRCC Cylinder Start Address DEBENDCC Cylinder and Address +8 DEBSTRHH Read or Write Track Start Address +10 +12 DEBENDHH Read or Write Track End Address +14 I I - No. of Tracks Allocated in this Extent +15 I I I I EXCP Access Method, BSAM t OSAM Dependent Section +0 +4 DEBVOLSQ Volume Sequence Number +2 DEBVOLNM No. of Volumes DEBDSNM (Only present when OPEN for a Member Name) +11 ~- ------- ........ -........ -- ... -----_ .... - ........ ------ ........................... --_ .............. --- .. -_ .............. -- .. -_ .. -.-- .. _-_ ........... --_ .... -_ ........ -_ ...... -_ ........ -- -- -_ .. -- . - ---- ... _--- ...... -- .. ---- .......... -- -- --.- ---------_ .. -- --_ -_ ........ -_ ........ --- ----- ---_ .. ----- --~ Figure 8. Data Extent Block -- Ordinary (Part 2 of 4) .... DEB 85 DATA EXTENT BLOCK -- ORDINARY --·BPA-M·-O-ep-e·nde·rlt--Secti 0 n5-·--------------·-··--·---·--·-····-··········-····-..-.-..-....-..--.-..-.-.....-.-.--.... -...-......--............................-.-...-.-j -·~~f--~···- +0 .--..-_. -. ---~---~---- .-----.-. -. -. -. -. -. -. - --- - -- -- -- -- -- -- -- -- -- -- . DEBEXTNM I I I Output +0 DEBDSNAM Member Name (Only present when OPEN for a Member Name) , I +7 I L~eDA~§!.~tJ.~1!.. ____ . . _~ ___ ~ _____________ . ______________________________________ j i Fixed-Length Records, Relative Block Addressing (No Track Overflow) +0 B/T No. of Blocks Per Track I +1 r-- B/E: No. of Blocks Per Extent +3 l~ I I Fixed -Length Records, Relative Block Addressing Track Overflow +0 TIP No. of Tracks Per Period +4 B/P No. of Blocks Per Period +8 B/E No. of Blocks Per Extent +11 I I - l I L -__._. _____ .__ .. ______ .___._________ ._____________________________ . __________ .J ~ BTAM Section +0 Address of Buffer Routine - +4 Address of First CCWon Queue , I I I GAM Section Reserved I I-- r-- I +0 I I Figure - DEBUCBAD Address of UCB +3 ~ I 1.. - - _ - __ .. ____ .. _____ ..... __________ ............. _______ .. _______ ... ____ ..... _ .......... ____ ....... ___ ........ ____ ............ ___ ...... _ ....... ______ .. _ .. _ .. __ ...... ___ .... _ .. ___ ............. __ .. ___ oo 86 +7 8. Data Extent Block -- Ordinary -- OS System Control Blocks .. _ _ _ _ .. _ . . . . . . . . . . . . . . . . . . . . . . . _ (Part 3 of 4) . . . . . . . . . . . . _ _ . . . . . . _ _ ................ _ _ _ _ . . . . _ _ . . . . _ _ .. _ .. _ _ .. _ _ _ oo .. _ _ _ _ .. ( DATA EXTENT BLOCK -- ORDINARY Subroutine Name Section +0 DEBSUBID Subroutine ID --+1 ~I-------------- I - I Figure 8. Data Extent Block -- Ordinary (Part 4 of 4) ) DEB 87 DATA EXTENT BLOCK -- ORDINARY Offset Bytes and Aliqrunent Field Name Field Description, Contents, Meaning APPENDAGE TABLE BSAM, QSAM, BPAM, BDAM, GAM -36 (-24) 4 (End of Extent) Address of the end-of-extent appendage routine. -32 (-20) 4 (start I/O) Address of the start I/O appendage routine. -28 (-lC) 4 (PCI) Address of the program-controlled-interruption appendage routine. -24 (-18) 4 (Channel End) Address of the channel-end appendage routine. -20 (-14) 4 (Abnormal End) Address of the abnormal-end appendage routine. BTAM, QTAM MESSAGE CONTROL -36 (-24) 4 DEBEOEA Address of the end-of-extent appendage routine. -32 (-20) 4 DEBS lOA Address of the start I/O appendage routine. -28 (-lC) 4 DEBPCIA Address of the program-controlled-interruption appendage routine. -24 (-18) 4 DEBCEA Address of the channel-end appendage routine. -20 (-14) 4 DEBXCEA Address of the abnormal-end appendage routine. END OF APPENDAGE TABLE PREFIX SECTION DIRECT-ACCESS STORAGE DEVICES -16 (-10) 1 DEBWKARA I/O Support work area. -15 • 7 DEBDSCBA DSCB address (BBCCHHR) used by I/O support. (-9) ALL DEVICES -8 (-8) 4 DEBDCBMK DCB modification mask used by I/O support .• -4 (-4) 1 DEBLNGTH Length of DEB in double words. -3 (-3) • 3 Reserved ( 88 OS System Control Blocks DATA EXTENT BLOCK -- ORDINARY Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DEB PROPER BASIC SECTION o (0) 1 1 (1) • 4 (4) 1 5 (5) • 8 (8) 1 3 3 DEBNMSUB Number of subroutines loaded by the open executor routines. DEBTCBAD Address of the TCB for this DEB. DEBAMLNG Number of bytes in the access method dependent section. For BDAM this field contains the length expressed in number of words. DEBDEBAD Address of the next DEB in the same task. DEBOFLGS Data Set status flags. 01 •• 10 •• 11 •• •• 1. ••• 1 1 ... .1 .. •• 1. •.• 1 9 (9) • 12 (C) 1 3 Disposition is OLD Disposition is MOD Disposition is NEW EOV or EOF Release unused external storage DCB modification Split cylinder Nonstandard labels Magnetic Tape Devices: Use reduced error recovery procedure. DEBIRBAD IRB storage address used for appendage asynchronous exits. DEBOPATB The method of input/output processing and the disposition that is to be performed when an end of volume condition occurs. 00 •• •• 01 •• 11 0000 1111 0011 0111 0001 0100 DEBQSCNT (always zero) REREAD LEAVE INPUT OUTPUT INOUT OUTIN RDBACK UPDAT PURGE (SVC 16) - Quiesce count. Number of devices executing user's channel programs, as shown by bits 5 and 6 of UCBFLl fields. 13 (D) • 1 14 (E) •• 2 16 (10) 1 DEBNMEXT Number of extents specified in the DSCBs. 17 (11) • 3 DEBUSRPG Address of first lOB in the user purge chain. 20 (14) 1 DEBPRIOR priority of the task. 21 (15) • 3 DEBECBAD Address of a parameter list used to locate the purge ECB for an SVC purge request. Reserved DEB 89 DATA EXTENT BLOCK -- ORDINARY Offset Bytes and Alignment Field Name Field Description, Contents, Meaning BASIC SECTION (Continued) 24 (18) 1 DEBPROTG, DEBDEBID xxxx 1111 Protection key. A hex nF" to identify this block as a DEB. 25 (19) • 3 DEBDCBAD Address of DCB associated with this DEB. 28 (lC) 1 DEBEXSCL Extent scale: 4 for direct access device and 2 for nondirect access device and communication device. This field is used to determine the size of the Device Dependent Section. 29 (lD) • 3 DEBAPPAD Address of the I/O appendage vector table. ISAM DEPENDENT SECTION Present only if ISAM is used. Follows the basic section. Precedes the device dependent section. 32 (20) 1 DEBNIEE Number of extents of independent index area. 33 (21) • 3 DEBFIEAD Address of first index extent. 36 (24) 1 DEBNPEE Number of extents of prime data area. 31 (25) • 3 DEBFPEAD Address of the first prime data extent. 40 (28) 1 DEBNOEE Number of extents of independent overflow area. 41 (29) • 3 DEBFOEAD Address of the first overflow extent. 44 (2C) 4 DEBDISAD Address of privileged module entered when a BISAM macro instruction is executed. DEVICE DEPENDENT SECTION Follows the basic section, except in ISAM. follows the ISAM dependent section. In ISAM, UNIT RECORD AND MAGNETIC TAPE 32 (20) 1 DEBDVMOD Device Modifier. Magnetic Tape -- SET MODE operation code. Unit record -- Not used. 33 (21) • 3 DEBUCBAD Address of a UCB associated with a given data set. TELECOMMUNICATIONS DEVICES 32 (20) n times List of addresses (n) of UCBs for lines (n). 1 Reserved • 3 DEBUCBAD Address of the UCB for the line. ( 90 OS System Control Blocks DATA EXTENT BLOCK -- ORDINARY Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DIRECT-ACCESS STORAGE DEVICES EXTENT DESCRIPTION SEGMENTS: For each extent there is a 16-byte segment as follows. +0 1 +1 · +4 2 +6 '. · +8 2 3 +10 '. · +12 2 +14 ·· 2 2 2 DEBDVMOD Device modifier: file mask. DEBUCBAD Address of UCB associated with this data extent. DEBBINUM Bin number. DEBSTRCC Cylinder address for the start of an extent limit,. DEBSTRHH Read/Write track address for the start of an extent limit. DEBENDCC Cylinder address for the end of an extent limit. DEBENDHH Read/Write track address for the end of an extent limit. DEBNMTRK Number of tracks allocated to a given extent. ACCESS METHOD DEPENDENT SECTION Follows the device dependent section, except for ISAM. The ISAM dependent section precedes the device dependent section. BSAM, QSAM, EXCP Access Method +0 2 DEBVOLSQ Volume sequence number for multivolume sequential data sets. +2 • • 2 DEBVOLNM Total number of volumes in a multivolume sequential data set. +4 8 DEBDSNM Member name. This field appears only when an output data set has been opened for a member name and the DSCB specifies a partitioned data set. Only one of the following fields is present: +0 (m-l)x1 DEBEXTNM For a partitioned data set opened for input, each one byte field contains the extent number of the first extent entry for each data set except the first, if two or more data sets (m) are concatenated. The number of bytes in the field is equal to one less than the number of data sets concatenated. +0 8 DEBDSNAM For a partitioned data set opened for output for a member name, this field is the member name. DEB 91 DATA EXTENT BLOCK -- ORDINARY Offset Bytes and Alignment Field Name Field Description., Contents, Meaning Only present for fixed-length records with the option of relative block addressing (but not track overflow) There is one of these four byte fields for each extent described in the device dependent section. +0 1 B/T Number of blocks per track,. +1 '. 3 B/E Number of blocks per extent. Only present for fixed-length records with the option of relative block addressing and track overflow These fields occur only once within a DEB: +0 4 T/P Number of tracks per period. +4 4 B/P Number of blocks per period. The following field occurs once for each extent: +8 4 B/E Number of blocks per extent. This segment is always present for BTAM. It is used when a buffer pool or dynamic buffering is used; else the fields are zero. +0 4 Address of the buffer routine. +4 4 Address of the first 4 n times ccw on the queue. Address of following CCWs on the queue. GAM +0 1 +1 • 3 Reserved. DEBUCBAD1. Reserved 1 '. 3 Pointer to first UCB. DEBUCBADn Pointer to last UCB. SUBROUTINE NAME SECTION Follows the access method dependent section, or the device dependent section if there is no access method dependent section.. n times +0 DEBSUBID 2 Subroutine Identification. Each access method subroutine. appendage subroutine, and IRB routine will have a unique eight-byte name. The low-order two bytes of each routine name will be in this field if the subroutine is loaded by the Open routines. ( 92 OS system Control Blocks Data Extent Block-QTAM Message Processing Program This data extent block is used in QTAM by a message processing program to describe message process queues and destination queues, which are in main storage. (BTAM, and QTAM message control programs, use the ordinary DEB described previously.) It is an extension of the information in the DeB concerning the physical characteristics of the data set and other information that is used by the control program. Figure 9A shows the format of the DEB proper used for message processing queues; Figure 9B shows the DEB for destination queues. DEB -- QTAM 93 DATA EXTENT BLOCK -- QTAM Prefix -16 (-10) Work area 1- 15 (-F) DSCB Address -8 (-8) DCB Mask -4 (-4) 1-3 (-3) Reserved Length -1 (-1) Basic Section 1 (1) 0(0) Address of TCB Reserved 5 (5) 4 (4) Address of Next DEB Reserved ~ 1...8 (8) ~ -r- ~r- Reserved 17 (11) Address of Next Record 21 (15) 20 (14) Address of Next DEB Reserved 25 (19) 24 (18) ID Address of DCB 29 (10) 28 (lC) Address of DEB + 48 Reserved 32 (20) 35 (22) 1st Word of Dummy LCB Queue Control Block 36 (24) 137 (25) Address of Dummy Entry Reserved 40 (28) Reserved 145 (2D) Address of QPRIRITY Subtask 47 (2F) Buffer Request Block 48 (30) Reserved 53 (35) 52 (34) Reserved Priority 57 (39) 56 (38) Address of QCB Op Code 61 (3D) 60 (3C) Address of DEB Hex Code + 32 63 (3F) 66 (42) 64 (40) Size of Work Area Reserved T 87 (57)T Figure 9A. Data Extent Block -- QTAM -- Message Process Queue ( 94 OS System Control Blocks DATA EXTENT BLOCK -- QTAM Prefix -16 (-10) 1-15 (-F) Work Area DSCB Address -8 (-8) DCB Mask -4 (-4) 1-3 (-3) Length -1 (-1) Reserved Basic Section 0(0) 1 (1) Address of TCB Reserved 4 (4) 5 (5) Address of Next DEB Reserved 8 (8) ~'- -~ ~r- Reserved ~~ 21 (15) Address of Next DEB 24 (18) 25 (19) Address of DC B ID 28 (lC) 31 (IF) Reserved Queue Control Block ---I~!!t~~:~!~£::~!~~E:::::::=:::::::::::::::::::::::::::::::::::::::::::R~,.e~.~:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::}:l-! f"""" Line Block -_ . . . .Control . . . . . ------.............. -_ . --.. . ---------.. --_. . ----_ . -_ . --........ ----.. . -----.. ---------_ . ------.. . ---.. ---.. . ----.. . -----...................... -_ . --.. . -_ . -_ . ---.. --............ ------............ -----_ . --................ ----roOi .... !i--.. -: ~ _~ , i! 28 40 ( bondHion Cod. 41 (29) Adde... of QPRIRITY S,bto,k 43 (2B) I I j l -----r--r-------------------------------------------------------------------~-------------------------------------------------------------------------------------------------------------------, 11144 (2C) l~~) I .....- -~ 47 (2F)1 Reserved 1 I Reserved 69 1 (45) Adde... of OCB 72 (48) - ~ Save Area 84 (54) 185 (55) Reserved 186 (56) Message Priority Reserved 87 (57) : ' 1. _ _ _ _ _ - - - - - - - - - - - - - - - - _ ... _ - _ ...... _ - _ ... - - - - - - - - - - - - - - - - - - - - - - - - ... - - - .. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ... _ _ _ _ _ _ _ _ ... _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .. ' Figure 9B. Data Extent Block -- QTAM -- Destination Queue DEB -- QTAM 95 DATA EXTENT BLOCK -- QTAM Offset Bytes and Alignment Field Description, Contents, Meaning MESSAGE PROCESS QUEUE PREFIX -16 (-10) 1 Work area used by I/O support routines. -15 (-F) • 7 Direct access device address used by I/O support routines. (BBCCHHR) -8 (-8) 4 DCB modification mask used by I/O support routines. -4 (-4) 1 Length of this DEB. -3 (-3) • 3 Reserved Format DEB PROPER BASIC SECTION 0 (0) 1 Reserved 1 (1) • 3 Address of the TCB. 4 (4) 1 Reserved 5 (5) • 3 Address of the next DEB in the same task. 8 (8) 9 Reserved 17 (11) • 3 Address of the next available record of the process queue on the direct access device. 20 (14) 1 Reserved 21 (15) · 24 (18) 1 X'OF'; identifies this block as a DEB. 25 (19) • 3 Address of the DCB. 28 (lC> 1 Reserved 29 (lD) • 3 Address of the beginning of the buffer request block (BRB) portion of this DEB. 32 (20) 4 Address of a dummy LCB. 3 Address of the next DEB on the chain of the process program's DEBs. QUEUE CONTROL BLOCK 36 (24) 1 Reserved 37 (25) • 3 Address of dummy last entry in queue. 40 (28) 5 Reserved 45 (2D) • 3 Address of QPRIRITY subtask. c 96 OS System Control Blocks DATA EXTENT BLOCK -- QTAM Offset Bytes and Aligrunent Field Description, Contents, Meaning BUFFER REQUEST BLOCK 48 (30) 4 Reserved 52 (34) 1 Priority 53 (35) • 3 Reserved 56 (38) 1 X'08'; identifies the operation code for a TIC command. 57 (39) • 3 Address of the process queue control block on the direct access device. 60 (3C) 1 X'07'; indicates a dummy buffer request block. 61 (3D) '. 3 Address of the beginning of the line control block portion of this DEB. END OF BUFFER REQUEST BLOCK 64 (40) 2 Size of work area necessary for GET. 66 (42) '• • 22 Reserved DESTINATION QUEUE PREFIX -16 (-10) 1 Work area used by I/O support routines. -15 (-F) • 7 Direct access device address used by I/O support routines. (BBCCHHR) -8 (-8) 4 DCB modification mask used by I/O support routines. -4 (-4) 1 Length of this DEB. -3 (-3) • 3 Reserved Format DEB PROPER BASIC.SECTION o (0) 1 1 (1) .• 4 (4) 1 Reserved 5 (5) .. 3 Address of the next DEB in the same task. 8 (8) 13 Reserved 21 (15) • 3 Address of the next DEB on the chain of proceSSing program's DEBs 24 (18) 1 X'OF' identifies this block as a DEB. 25 (19) '. 3 Address of the DCB. 28 (lC) 4 Reserved Reserved 3 Address of TCB. DEB -- QTAM 97 DATA EXTENT BLOCK -- QTAM Offset Bytes and Alignment Field Description, Contents, Meaning BUFFER REQUEST BLOCK, QUEUE CONTROL BLOCK 32 (20) 8 Reserved LINE CONTROL BLOCK 40 (28) 1 Condition code from the line control block. 41 (29) • 3 Address of QPRIRITY subtask. END OF QUEUE CONTROL BLOCK 44 (2C) 4 Reserved END OF BUFFER REQUEST BLOCK 48 (30) 21 Reserved 69 (45) • 3 Address of the queue control block for the destination queue. 72 (48) 12 Save area. 84 (54) 1 Reserved 85 (55) • 1 Temporary location for the message priority code. 86 (56) 2 Reserved END OF LINE CONTROL BLOCK END OF QTAM DEB 98 OS System Control Blocks Data Event Control Blocks Data event control blocks (DECB) contain information about an input or output operation requested by a READ or WRITE macro instruction. separate diagrams and descriptions are presented for the following uses of DECBs: • BSAM • ISAM • BDAM • QTAM • BTAM DECB 99 Data Event Control Block-BSAM The data event control block (DECB) is created when a READ or WRITE macro instruction is expanded. It contains information about the input or output operation that is requested by the macro instruction. Figure 10 shows the format of the DECB used in BSAM. Descriptions of the fields follow the illustration. DECB -- BSAM 101 DATA EVENT CONTROL BLOCK -- BSAM 0(0) DECSDECB Event Control Block 6 (6) 4 (4) DECLNGTH Length of Key and Data DECTYPE Type of I/o Request 8 (8) DECDCBAD Address of DCB -----'-"""'-"--- 12 (C) DECAREA Address of Key and Data 16 (10) DECIOBPT Address of lOB Figure 10. Data Event Control Block -- BSAM DATA EVENT CONTROL BLOCK -- BSAM Offset Bytes and Alignment Name Field Field Description, Contents, Meaning o (0) 4 DECSDECB Event control block. 4 (4) 2 DECTYPE Type of I/O request. 4 (4) Byte 1 1 ••• .xxx xxxx Byte 2 5 (5) 1 ••• Type of length operand: S coded for length. (Reserved bits) Type of operation: SF READ SB WRITE SF WRITE SD (Reserved bits.) WRITE SZ READ .1,•• •• 1. • ,•• 1 x.xx .1 •. 6 (6) •• 2 DECLNGTH Length of key and data. 8 (8) 4 DECDCBAD Address of the DCB to which this I/O request is related. 12 (C) 4 DECAREA Address of the key and data. 16 (10) 4 DECIOBPT Address of the lOB. 102 OS System Control Blocks 19 (13) Data Event Control Block-ISAM The data event control block (DECB) is created when a READ or WRITE macro instruction is expanded. It contains information about the input or output operation that is requested by the macro instruction. Figure 11 shows the format of the DECB used in ISAM. Descriptions of the fields follow the illustration. DECB -- ISAM 103 DATA EVENT CONTROL BLOCK -- ISAM 0(0) DECBECB Event Control Block 5 (5) 4 (4) DECBTYPI Options 6 (6) DECBLGTH No. of Bytes Read or Written DECBTYP2 Type of I/o 8 (8) DECBDCBA Address of DCB 12 (C) DECBAREA Storage Address for Record 16 (10) DECBLOGR Address of Logical Record 20 (14) DECBKEY Address of Key Portion of Record 24 (18) DECBEXCI Exceptional Condition Codes Figure 11. 104 25 (19) DECBEX2 Exceptional Condition Codes Data Event Control Block -- ISAM OS System Control Blocks DATA EVENT CONTROL BLOCK -- BISAM Offset o (0) o (0) Bytes and Alignment Field Field Description, Contents. Meaning DECBECB 4 .xxx xxxx Awaiting completion of the event. Flag field. Awaiting completion of the event. (Reserved bits) Address of the RB for the program awaiting the event. Byte 1 1 ••. 1 (1) Byte 2-4 o (0) Byte 1 x.xx xxxx .1 1 (1) 4 (4) G • Byte 2-4 DECBTYPl 1 (5) • 1 After completion of the event: Flag field. (Reserved bits) Event has completed (normally or abnormally). If the event completed abnormally. fields DECBEXCl and DECBEXC2 will show the reason. Reserved Options: ••• 1 (Reserved bits) Length coded as '5' • Area coded as '5' • DECBTYP2 Type of I/O request. xxxx xx •• •• 1. 5 Event control block. 1 ••• READ K .x.x •• xx •• 1. (Reserved) READ KU. WRITE K• WRITE KN. 1 •.• • 1 •• 6 (6) •• 2 DECBLGTH Number of bytes read or written. 8 (8) 4 DECBDCBA Address of the data control block. 12 (C) 4 DECBAREA Address of the area in storage for the record. 16 (10) 4 DECBLOGR Address of the logical record. 20 (14) 4 DECBKEY Address of the key portion of the record. 24 (18) 1 DECBEXCl Exceptional condition code. 1 ••• • 1 •• •• 1. .•. 1 1 ••• • 1 •. •• 1. ••• 1 25 (19) • 1 DECBEXC2 xxx x xxx. ••• 1 Record not found. Record length check • Space not found in which to add a record • Invalid request • Uncorrectable I/O error. Unreachable block • Overflow record • Duplicate record presented for inclusion in the data set. Exceptional condition code. (Reserved bits) Previous macro instruction was READ KU • ) DECB -- ISAM 105 ( Data Event Control Block-BDAM The data event control block (DECB) is created when a READ or WRITE macro instruction is expanded. It contains information about the input or output operation that is requested by the macro instruction. Figure 12 shows the format of the DECB used in BDAM. Descriptions of the fields follow the illustration. DECB -- BDAM 101 DATA EVENT CONTROL BLOCK -- BDAM 0(0) DECSDECB Event Control Block 4 (4) 6 (6) DECTYPE Type of I/O Request 8 (8) DECLNGTH Length of Data DECDCBAD Address of DCB 12 (C) DECAREA Address of the Data 16 (10) DECIOBPT Address of the lOB 20 (14) DECKYADR Address of the Key 24 (18) DECRECPT Address of Block Reference Field Figure 12. 108 Data Event Control Block -- BDAM as System Control Blocks 27 (1 B) DATA EVENT CONTROL BLOCK -- BDAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DECSDECB Event control block. o (0) o (0) Byte 1 1 ••• • xxx xxxx 1 (1) Byte 2-4 o (0) Byte 1 x.xx xxxx 4 • 1,•• 1 Byte 2 1 ••• • 1 •• • .1. ••• 1 (1) 1 ••• • 1 •• •• 1. ••• 1 2 Byte 3 x ••• ( 2) .1 .. •• 1. • •• 1 1 ••• .1 •• • .• 1. ••. 1 3 (3) 4 (4) 4 (4) Byte 4 DECTYPE 1 1 ••• .1 •• • .1 • •• • 1 1 ••• • 1 .. • .1. ••• 1 5 (5) • 1 1 ••.• • 1 •. • .xx • '. ,.x x ••• 0 ••• 1 ••• .x •• • 0 •• • 1 .• •• 1. Awaiting event completion. waiting for completion of event. (Reserved bits) Address of the request block for the program waiting for completion of the event. After event completion: (Reserved bits) Event has completed • Record not found. Record length check • Space not found,. Invalid request. (This condition also sets a bit in the next byte.) Uncorrectable I/O error. End of data • Uncorrectable error other than an I/O error • A READ with exclusive control was not preceded by a WRITE with exclusive control. (A reserved bit) A WRITE macro instruction was addressed to an input data set. An extended search was specified with the DCBLIMCT field set to zero. The block requested is not within the data set. A write-by-identification (DI) addressed record zero. A search-on-key (DK) was specified with the DCBKEYLE field set to zero or without an address for the key. A macro instruction used an option not set in the DCB. The key for the fixed-length record to be added begins with hex. FF. Reserved Type of I/O request. Verify. Overflow. Extended search. Feedback. Actual addressing. Dynamic buffering • Read exclusive. Relative block addressing • S coded for key address. S coded for block length • (Reserved bits.) Type of operation WRITE READ Type of search argument Id • Key. Add option of WRITE operation • DECB -- BDAM 109 DATA EVENT CONTROL BLOCK -- BDAM Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DECLNGTH Length of the data. 6 (6) .. 8 ( 8) 4 DECDCBAD Address of the DCB to which this I/O request is related. 12 (C) 4 DECAREA Address of the data. 16 (10) 4 DECIOBBT Address of the IOB. 20 (14) 4 DECKYADR Address of the key. 24 (18) 4 DECRECPT Address of the Block Reference Field. 110 2 OS System Control Blocks Data Event Control Block-QTAM The data event control block (DECB) is created when a READ or WRITE macro instruction is expanded. It contains information about the input or output operation that is requested by the macro instruction. Figure 13 shows the format of the DECB used in QTAM. Descriptions of the fields follow the illustration. DECB -- QTAM 111 DATA EVENT CONTROL BLOCK -- QTAM 0(0) LlNEDECB Always Zero 4 (4) 5 (5) 16 (6) Reserved Op Code Length of Input Area 8 (8) Address of DCB 12 (C) Address of Data in Buffer 16 (10) Reserved 20 (14) 21 (15) No. Messages Received 24 (18) Address of Active Entry in Polling List 25 (19) Reserved 126 (lA) Index, in DEB, to UCB Reserved 28 (1C) Reserved 32 (20) Address of Addressing Characters in Terminal Entry 36 (24) 37 (25) Reserved eFigure 13. Offset Address of Poll i ng List 39 (27) Data Event Control Block -- QTAM Bytes and Alignment Field Name Field DescriQtion, Contents, Meaning LINEDECB Always zero. 0 (0) 4 4 (4) 1 5 (5) · 6 (6) 8 (8) 4 Address of the DCB. 12 (C) 4 starting address for data in a buffer. 16 (10) 4 Reserved 20 (14) 1 Number of messages received. 21 (15) 24 (18) 1 Reserved 25 (19) ·1 Index to the UCB address in the DEB. 26 (lA) 28 (lC) 4 Reserved 32 (20) 4 Address of the addressing characters in the terminal entry. 36 (24) 1 Reserved 37 (25) ·3 Address of the polling list. Reserved Operation code for the current segment. 1 2 3 Length of input area for the initial read. Address of currently active entry in the polling list. 2 Reserved c 112 OS System Control Blocks Data Event Control Block-BTAM The data event control block (DECB) is used in the execution of a READ or WRITE macro instruction. It contains information about the input or output operation that is requested by the macro instruction. Figure 14 shows the format of the DECB. Descriptions of the fields follow the illustration. DECB -- BTAM 113 DATA EVENT CONTROL BLOCK -- BTAM 0(0) DECSDECB Event Control Block 4 (4) 6 (6) DECTYPE Programming, Indicators, Code 8 (8) DECBUFCT Buffer Count 9 (9) DECBLNGTH Buffer Length, Message Area Length DECDCBAD DCB Address 12 (C) DECAREA Buffer Address, Message Area Address 17(11) 16 (10) 18 (12) DECSENSO Sense Byte DECSENS 1 Reserved 20 (14) DECCOUNT CSW Residual Count DECCMCOD, DECENTRY Error Command, Terminal List Address 24 (18) DECFLAGS Operations Status 28 (lC) DECTPCOD Operation 25 (19) 26 (1A) DECRLN Relative Line No. 29 (lD) DECRESPN Addressing Response, VRC/LRC Response 30 (1 E) DECERRST Error Status DECCSWST CSW Status I/o 32 (20) DECADRPT Address of Previous Entry in Addressing List 36 (24) DECPOLPT Contents Depend on Use of Autopoll, Programmed Polling, or BSC B SC Extension 42 (2A) 40 (28) Reserved 44 (2C) • Figure 14. 114 DECWAREA Data Area Address Data Event Control Block -- BTAM OS System Control Blocks DECWLNG Data Area Length 47 (2F) Offset Bytes and Alignment Field Name DATA EVENT CONTROL BLOCK -- BTAM Hex. Dig. Field Description, Contents, Meaning o (0) 4 DECSDECB Event control block. 4 (4) 2 DECTYPE Programming indicators. 4 (4) Byte 1 xx •• Except during BSC on-line test: READ, using Autopoll (Reserved bit) During BSC on-line test: Qn-line test, requested by RFT message. on-line test, initiated by ONLTST macro instruction. Sending text messages • Receiving text messages • (Reserved bits) 'Sf coded for terminal entry • 'Sf coded for area • 'Sf coded for length • 1 ••• .• x ... xx •• 0 ••• 1 ••• • 0 •• • 1 •• •• xx x ••• . 1 •• • • 1. ••• 1 Command Code 5 (5) Byte 2 00 01 02 03 04 05 06 07 07 08 09 OA OB OC OD OE OF 10 11 12 13 14 15 16 17 19 lA lD lF 82 83 84 85 86 87 89 8C 92 94 write break. Read initial .• Write initial. Read continue. Write continue. Read conversational. write conversational. Read repeat (other than WTTA). WTTA: Read continue with identification change. Write acknowledge. Read skip. Write negative acknowledge, Write reset (BSC). Read buffer. Write at line address. Write initial conversational. Write erase. Write continue conversational. Write disconnect. Read stop. Write initial transparent. Read continue with leading graphics. Write continue transparent. Read inquiry. Write inquiry .• Read repeat with leading graphics. Read initial inquiry. Write wait before transmitting. Write initial conversational transparent. Write continue conversational transparent. Write initial with reset. Read continue with reset. Write continue with reset. Read conversation with reset. TVR Write conversation with reset. TPR Read repeat with reset. TSR Read skip with reset. TLR Write at line address with reset. TIXR Write initial transparent with reset. TTXR write continue transparent with reset. TB TI TI TT TT TV TV TP TE TA TS TN TR TB TL TIV TS TTV TD TTS TIX TTL TTX TQ TQ TPL TIQ TW TIVX TTVX TIR TTR TTR TVR DECB -- BTAM 115 Offset Bytes and Alignment Field Name DATA EVENT CONTROL BLOCK -- BTAM Hex. Dig. Field Description, Contents, Meaning 6 (6) •• 2 DECLNGTH Length of buffer or message area. 8 (8) 1 DECBUFCT contains a running count of buffers obtained by BTAM for the current Read or Write operation. (Dynamic buffering only.) 9 (9) · DECDCBAD Address of associated DCB. 12 (C) 4 DECAREA Address of buffer or message area. 16 (10) 1 DECSENSO Sense information. 17 (11) • 1 DECSENSl Reserved 18 ( 12) · DECCOUNT Residual count from CSW for last CCW executed. 20 (14) 1 21 (15) · 24 (18) 1 3 • 2 DECCMCOD, DECENTRY Command for which the error occurred. 3 DECENTRY Address of the terminal list. DECFLAGS Operation status. xxx ••••• 1 ••• • 1 •• •• 1. ••• 1 1 •.• .• 1 •• •• x • ••• 1 116 OS System Control Blocks One of These: Start-Stop Operations (Reserved Bits) BSC Operations: SAK received. Incorrect acknowledgement received • Acknowledgment alteration incorrect • One of These: TWX 33/35 terminal, BSC terminal: Incorrect ID received. Autopoll: Index byte received does not match an active one. BSC network: Contention occurred. WTTA: Contention occurred. READ, dynamic buffering: No buffer was available. (Message lost.) One of These: OPENLST, POLLING: Negative response to polling received. WRAPLST: All entries are inactive. Addressing: Negative response to addressing received. WTTA: Last message received ended with EOT or time-out. (A reserved bit.) WTTA: Last message received ended with WRU. Offset Bytes and Alignment Field Name DATA EVENT CONTROL BLOCK -- BTAM Hex. Dig. Field Description, Contents, Meaning 25 (19) • 1 DECRLN Relative line number. 26 (lA) •• 2 DECRESPN Response indicators (One of these). 26 (lA) Stop - start Operations: Response from a terminal to addressing,. vertical redundancy character and longitudinal redundancy character (VRC/LRC) response. Byte 1 Byte 2 26 (lA) 28 (lC) 1 BSC Operations: Response from a terminal to addressing. Type of Terminal DECTPCOD 00 on-line test,. 01 Disable when disable is the first command of a channel program. Dial. Enable. Prepare. Write pad character. Write wait before transmitting. 02 WTTA 2740, Basic 03 TWX TWX,BSC Sense Write control characters @ © © before selection. Write EOT sequence before polling or addressing. Write response to text. Write @ and 15 idle characters. © Write polling, addressing, or broadcast characters. Poll write inquiry. Write turn around sequence. Write CPU-ID sequence. 04 2740 w/st.c 2260R 83B3 1030 WTTA 05 Read response to polling. (DECTPCOD 06 Continues) Write space (w/st.c. - with station control). Write 2848 command. Write FIGS shift. Write 1. Write WRU. Write Identification. Write padding characters. Write letter shift characters. Read response to addressing. DECB -- BTAM 117 Offset Bytes and Alignment Fi el d Name DATA EVENT CONTROL BLOCK -- BTAM Hex,. Dig,. Field Description, Contents, Meaning Type of Terminal 28 (lC) (DECTPCOD 07 Continued) 08 TWX,BSC 1030 1050 2740 1060 2260 BSC Read ID response .• write end-of-addressing character after addressing. write response to Inquiry. write response to text. write EOT, SYN, SYN, SYN, before polling or addressing. 09 NOP or TIC after Poll in a READ with SSALST, SSAWLST, AUTOLST, or AUTOWLST. OA Read Index (auto poll). Read response to polling (Programmed polling). OB BSC Read inquiry. OC BSC Read response to inquiry. 10 2260R write at line address. 11 Read or write text. 12 Read skip or TIC for dynamic buffering. 13 BSC write end-of-transparent-text characters. 20 start - Stop read response to text. 21 All reset commands. 22 Read skip. 23 write break. 24 V open, LOPEN or close routine operation. 25 BSC Read response to text. 40-4C 50-53 61-65 ,The last ccw executed was the first Read or Write Text CCW to be executed in a channel program using dynamic buffering. 80-8C 90-93 Al-A5 The last CCW in a channel program was executed. c 118 OS System Control Blocks Offset 29 (lD) Bytes and Alignment • 1 Field Name DATA EVENT CONTROL BLOCK -- BTAM Hex. Dig. Field Description, Contents, Meaning DECERRST 1 .... • 1 •• '•. 1 .. ... 1 1 •.• ••••• xxx I/O error status flags. SIO resulted in a condition code of 3. Undefined error condition • An error condition occurred during an I/O operation initiated by the error recovery routines. Diagnostic Write/Read operation ended because of error, (2701 only). Disable command issued to a switched-connected line by error recovery routine because of permanent error on that line. (Reserved bits) 30 (lE) •• 2 DECCSWST status bits from CSW for last CCW executed. 32 (20) 4 DECADRPT Address of addressing list entry used in previous operation. 36 (24) 4 DECPOLPT One of these: Programmed Polling: Address of the current entry in the polling list. Autopoll: Byte 1: Indexed to current entry in polling list. Bytes 2-4: Address of polliqg list. BSC On-Line test: Address of text data. BSC Extension Fields are present only if BSC is specified in the OPEN macro instruction. 40 (28) 2 42 (2A) •• 2 DECWLNG Length, in bytes, of the data area in leadinggraphics and conversational type operations. 44 (2C) 4 DECWAREA Address of the data area in leading-graphics and conversational operations. Reserved DECB -- BTAM 119 ( Data Set Control Blocks The data set label for a data set residing on a direct access volume is called a data set control block (DSCB). One or more DSCBs are used to describe the data set. Each DSCB is 140 bytes, consisting of a 44 byte key and a 96 byte data portion. The DSCBs describing all data sets on a volume make up the Volume Table of Contents (VTOC> . separate diagrams and descriptions are presented for the following uses of DSCBs: • • • • • • DSCB DSCB DSCB DSCB DSCB DSCB Format Format Format Format Format Format 1 2 3 4 5 6 In addition, there is a format 0 DSCB. It has the same format as other DSCBsi however, it contains all binary zeros. DSCB 121 c Data Set Control Block-Format 1 This data set control block (DSCB) describes the characteristics and up to three extents of a data set. For data sets having indexed sequential (IS> organization, additional characteristics are specified in a format 2 DSCB pointed to by the format 1 DSCB. Additional extents are described in a format 3 DSCB pointed to by the format 1 DSCB (or format 2 when the data set has IS organization). A data set can have a maximum of 16 extents on one volume. Figure 15 shows the format of the format 1 DSCB. Descriptions of the fields follow the illustration. DSCB 123 DATA SET CONTROL BLOCK -- FORMAT 1 1 .., 10 (0) DSlDSNAM Data Set Name ............-r- 44 (2C) DS1FMTlD Format Identifier 45 (2D) 53 (35) Continued 56 (38) 60 (3C) DS1DSSN Data Set Serial Number DS1VOLSQ Volume Sequence No. 59 (3B) DS1NOEPV No. of Extents DS1CREDT Creation Date DS1EXPDT Expiration Date DS1NOBDB 51(33) 61 (3D) 62 (3E) Reserved --. - DS1SYSCD Programming System Code ID -'- -r- 75 (4B) Reserved 82 (52) Figure 15. DSlDSORG Data Set Organization Data set Control Block -- Format 1 (Part 1 of 2) ( 124 OS System Control Blocks DATA SET CONTROL BLOCK -- FORMAT 1 84 (54) DS1RECFM Record Format 88 (58) 85 (55) 86 (56) DS10PTCD Option Codes 90 (5A) DS1LRECL . Logical Record Length 93 (5D) Continued Continued 101 (65) Continued 104 (68) DSlDSIND Data Set Indicators DS1BLKL Block Length 91 (5B) DS1 KEYL Key Length DS1RKP Relative Key Position 94 (5E) DS1SCALO Secondary Allocation 98 (62) DS1LSTAR Pointer to Last Written Block DSlTRBAL LL Part of Disk Address 103 (67) Reserved 105 (69) Reserved DS1 EXTl First Extent Description 115 (73) _.... -- DS1EXT2 Second Extent Description _I-.. -r- 125 (70) DS1EXT3 Third Extent Description 135 (87) DS1PTRDS Direct-Access Address of Next DSCB 139 (8B) Figure 15. Data Set Control Block -- Format 1 (Part 2 of 2) DSCB 125 Offset o (O) 44 Bytes and Alignment Field ~ DATA SET CONTROL BLOCK -- FORMAT 1 Hex. Dig. Field Description, Contents, Meaning 44 DSIDSNAM Data set name. (2C) 1 DSIFMTID Format identifier - Hex Fl. 45 (2D) • 6 DSIDSSN Data set serial number. 51 (33) DSIVOLSQ Volume sequence number. 53 (35) • 3 DSICREDT Creation date, in the form ydd. y - year: 00 - 99, dd - day: 1- 366 56 (38) 3 DS1EXPDT Expiration date, in the form ydd (as above). If neither a retention period nor an expiration date has been specified, ydd is zero. 59 (3B) .... 1 DSINOEPV Number of separate extents in which the data set resides on this volume. 60 (3C) 1 DSINOBDB Number of bytes used in the last PDS directory block. 61 (3D) • 1 62 (3E) '• • 13 75 (4B) '... 7 82 (52) • 2 Reserved 2 DS1SYSCD System code to identify the programming system. Reserved DSIDSORG Byte 1 11. ".Ie . 1 .. '. • _.1,. Data Code IS PS DA ••• x xx •• • ,.1,. '.... 1 83 (53) 84 (54) Byte 2 xxxx xxxx 1 DSIRECFM 10. '. 01..•• 11,•• .. 1. • '. 1.1 1 ••• • 10. • 01. .. 00. .. ,•.• 0 85 (55) 86 (56) '. 1 2 PO U set organization. Indexed sequential organization. Physical sequential organization,• Direct organization • (Reserved bits) Partitioned organization • Unmovable - the data contains location dependent information. Reserved Record format,. Code -FFixed length record format. V Variable length record format,. U Undefined length record format. T Track overflow • B Blocked: may not occur with undefined (U) • S Fixed length record format: Standard blocks no truncated blocks or unfilled tracks are embedded in the dataset. Variable length record format: Spanned records. A ASA control character • M Machine control character • No control character • Always zero • DSI0PI'CD Option code - same as DCBOPTCD field in DCB. DSIBLKL Block length for fixed length records or maximum block size for variable or undefined length records,. c 126 OS System Control Blocks Offset 88 (58) 90 (SA) 91 (5B) 93 (5D) Bytes and Alignment 2 ·.1 . ·1 2 Field Name DATA SET CONTROL BLOCK -- FORMAT 1 Hex. Dig. Field Description. Contents, Meaning DS1LRECL Format F records: Record length. Format U records: Zero. Format V records Unspanned record format: Maximum record length. Spanned record format Records up to 32,756 bytes: Maximum record length,.. Records exceeding 32,756 bytes: X'8000'. DS1KEYL Key length. DSlRKP Relative key position in the data block .. DS1DSIND 1 •• '. •• 1 .. .... 1 .. x ... xxxx 94 (5E) 94 (5E) · .. 4 DS1SCALO Byte 1 01. '. 01 •• 10 •• 11 •• ,.,.xx 1 ••• • 1,•• ... 1. '. .• 1 Data set indicators. This is the last volume on which this data set normally resides Block length must always be a multiple of 8 bytes. Data set is security protected by a password .. (Reserved bits) secondary Allocation .. Allocation parameters. Type of request issued for the initial allocation and to be used for subsequent extensions .. Original request was: In tracks relative to a specific location. No secondary allocation will be allowed. In blocks (physical records). In tracks .. In cylinders. (Reserved bits) For a contiguous extent,. For the maximum contiguous extent on the volume • For the five (or less) largest extents that are greater than or equal to a specified minimum .. In records, to be rounded up to a cylinder boundary .. 95 (SF) 98 (62) •• 3 DS1KLSTAR The last-block pointer indentifies the last block written in a sequential or partitioned organization data set. It is in the format TTRLL (LL is defined under the next field name): TT - Relative address of track containing the last block .. R - Block number on that track. 101 (65) • 2 DS1TRBAL LL portion of the format given in DS1LSTAR. LL - Number of bytes remaining on track following the block. Note: If both fields contain binary zeros, the last block pointer does not apply. Byte 2-4 secondary allocation quantity. Number of blocks, tracks, or cylinders to be requested at end of data set when processing a sequential data set. ) DSCB 127 Offset 103 (67) 105 (69) Bytes and Alignment Field Name DATA SET CONTROL BLOCK -- FORMAT 1 Hex. Dig. Field Description. Contents. Meaning Reserved 2 • 10 DS1EXT1 Extent description for the first extent. This extent description is also used in format 3 and 4 DSCBs. Data set extent type indicator. 105 (69) Byte 1 00 01 02 04 40 80 81 Following 9 bytes do not indicate any extent. The extent contains the data blocks (user's blocks), or is a prime area (for IS data sets) The extent is an overflow area (for IS data sets only). The extent is an index area (for IS data sets only). The first extent description describes the user label extent. The extent described is sharing one or more cylinders with one or more data sets The extent described begins and ends on cylinder boundaries, i.e., the extent is composed of one or more cylinders. 106 (6A) Byte 2 Extent sequence number (M) 107 (6B) Byte 3-6 Lower limit of this extent (CCHH). 111 (6F) Byte 7-10 Upper limit of the extent (CCHH). 115 (73) .• '. • 10 DS1EXT2 Extent description for the second extent. mat as DS1EXTl field. 125 (7D) • 10 DS1EXT3 Extent description for the third extent. as DS1EXTl field. 135 (87) ••• 5 DS1PTRDS Pointer to a format 2 DSCB. if data set has IS organization, or pointer to a format 3 DSCB if data set has sequential, direct, or IS organization and more than 3 extents. This pointer has the format CCHHR. Same forSame format ( 128 OS System Control Blocks Data Set Con.trol Block-Format 2 This data set control block (DSCB) describes characteristics of a data set having indexed sequential organization. It is pointed to by a format 1 DSCB which contains additional data set characteristics and up to three extents descriptions,. Additional extents are described in a format 3 DSCB pointed to by the format 2 DSCB. Figure 16 shows the format of the format 2 DSCB. Descriptions of the fields follow the illustration. DSCB 129 DATA SET CONTROL BLOCK-- FORMAT 2 0(0) 1 (1) Hex Code DS22MIND Starting Address of Second-Level Master Index 8 (8) DS2L2MEN Ending Address of Second-Level Master Index 13 (D) DS23MIND Starting Address of Third-Level Master Index 20 (14) DS2L3MIN Ending Address of Third-Level Master Index 25 (19) Reserved - _J... -r 1 44 (2C) DS2FMTID Format Identifier 45 (2D) DS2NOLEV No. of Index Levels 46 (2E) DS2DVIND Master Index for these many tracks 50 (32) Continued 52 (34) DS2CYLOV No. of Tracks in Overflow 53 (35) DS2HIRIN Highest R of High-Level Index 54 (36) 56 (38) DS2RSHTR Last Data Record R on Shared Track 57 (39) 58 (3A) Continued 64 (40) DS2HIRTI Highest R of Track Index 61 (3D) DS2NOBYT No. of Bytes for Highest-Level Index DS21RCYL HHR of First Data Record On Each Cylinder DS2LTCYL HH of Last Data Record on Each Cylinder DS2HIRPR Highest R of Prime Data 55 (37) DS2HIROV Highest R of Overflow Tracks 59 (3B) Reserved DS2TAGDT No. of Delete Records DS2RORG3 No. of References to Succeeding Overflow Records 66 (42) DS2NOTRK No. of Bytes 67 (43) DS2PRCTR No. of Records in Prime Data Area 71 (47) Continued Figure 16. 47 (2F) Data Set Control Block -- Format 2 DS2STIND Indicators (Part 1 of 2) c 130 OS System Control Blocks DATA SET CONTROL BLOCK -- FORMAT 2 72 (48) DS2CYLAD Address of First Track of Cylinder Index 79 (4F) DS2ADLIN Address of First Track of Lowest-Level Master Index 86 (56) DS2ADHIN Address of First Track of Highest-Level Master Index 93 (5D) DS2LPRAD Address of Last Record in Prime Data Area DS2LTRAD Address of Last Entry in Track Index on Last Cylinder 101 (65) 106 (6A) 111 (6F) DS2LCYAD Address of Last Entry in Cyl inder Index DS2LMSAD Address of Last Entry in Master Index ~ -116 (74) DS2LOVAD Address of Last Record Written in Independent Overflow Area -- ::~ 124 (7C) DS2BYOVL No. of Bytes Left on Independent Overflow Track 126 (7E) DS2RORG2 No •. of Tracks Left on Independent Overflow Area 128 (80) DS20VRCT No. of Records in Overflow Area 130 (82) DS2RORG1 No. of Full Cylinder Overflow Areas 135 (87) 132 (84) Reserved DS2PTRDS Direct-Access Address of Next DSCB Figure 16. 139 (8B) Data Set Control Block -- Format 2 (Part 2 of 2) DSCB 131 Offset Bytes and Alignment Field Name DATA SET CONTROL BLOCK -- FORMAT 2 Hex. Dig. Field Description, Contents, Meaning o (0) 1 1 (1) • 7 DS22MIND Address of the first track of the second level master index in the form MBBCCHH. 8 (8) 5 DS2L2MEN CCHHR of the last active index entry in the second level master index. 13 (D) • 7 DS23MIND Address of the first track of the third level master index in the form MBBCCHH. 20 (14) 5 DS2L3MIN CCHHR-of the last active entry in the third level master index. 25 (19) • 19 44 (2C) 1 DS2FMTID Format identification for format 2 DSCB. "2". ) 45 (2D) • 1 DS2NOLEV Number of index levels. 46 (2E) '• • 1 DS2DVIND Number of tracks determining development of the master index. 47 (29) DS21RCYL HHR of the first data record on each cylinder. 50 (32) •• 2 DS2LTCYL HH of the last data track on each cylinder. 52 (34) 1 DS2CYLOV Number of tracks of cylinder overflow area on each cylinder. 53 (35) • 1 DS2HIRIN Highest possible R on a track containing high level index entries. 54 (36) '.. 1 DS2HIRPR Highest possible R on prime data tracks for form F records. 55 (7) ••• 1 DS2HIROV Highest possible R on overflow data tracks for form F records. 56 (38) 1 DS2RSHTR R of the last data record on a shared track. 57 (39) • 1 DS2HIRTI Highest possible R on an unshared track of the track index. 58 (3A) •• 1 59 (3B) 61 (3D) 64 02 Hex code 02 to avoid conflict with a data set name. Reserved • 3 • 2 (EBCDIC Reserved BS2TAGDT Number of records that have been tagged for deletion. • 3 DS2RORG3 Number of random references to overflow records other than the first overflow record. (40) 2 BS2NOBYT Number of bytes needed to hold the nighest-level index in main storage .• 66 (42) ,• • 1 BS2NOTRK Number of tracks occapied by the highest level index. 67 (43) ••• 4 DS2PRCTR Number of records in the Frime data area. ( 132 OS System Control Blocks DATA SET CONTROL BLOCK -- FORMAT 2 Offset 11 (47) Bytes and Alignment ••• 1 Field Field Description, Contents, Meaning DS2STIND x •• x xx •• . 1 •• •• 1. • . 1. • • •1 Status indicators. Reserved Key sequence checking is to be performed • An initial load has been completed • Last block full • Last track full • 72 (48) 7 DS2CYLAD Address of the first track of the cylinder index in the form MBBCCHH. 79 (4F) ••• 7 DS2ADLIN Address of the first track of the lowest level master index in the form MBBCCHH. 86 (56) •• 7 DS2ADHIN Address of the first track of the highest level index in the form MBBCCHH. 93 (5D) • 8 DS2LPRAD Address of the last record in the prime data area, in the form MBBCCHHR. 101 (65) • 5 DS2LTRAD CCHHR of the last normal entry in the track index on the last cylinder. 106 (6A) •• 5 DS2LCYAD CCHHR of the last index entry in the cylinder index. 111 (6F) DS2LMSAD CCHHR of the last index entry in the master index. 116 (74) 8 DS2LOVAD Address of the last record written in the current independent overflow area, in the form MBBCCHHR. 124 (7C) 2 DS2BYOVL Number of bytes remaining on the current independent overflow track. 126 (7E) •• 2 DS2RORG2 Number of tracks remaining in the independent overflow area. 128 (80) 2 DS20VRCT Number of records in the overflow area. 130 (82) •• 2 DS2RORG1 Number of cylinder overflow areas that are full. 132 (84) 3 • 5 Reserved 136 (88) ••• 5 DS2PTRDS Pointer to format 3 DSCB if a continuation is needed to describe this data set. This pointer has the format CCHHR. ) DSCB 133 ( Data Set Control Block-Format 3 This data set control block (DSCB) describes up to thirteen additional extents that cannot be described in a format 1 DSCB. It is pointed to by a format 1 or format 2 DSCB. Figure 17 shows the format of the format 3 DSCB. Descriptions of the fields follow the illustration. DSCB 135 DATA SET CONTROL BLOCK -- FORMAT 3 Key Identifier DS3EXTNT 4 Extent Descriptions 44 (2C) DS3FMTlD Format Identifier 45 (2D) DS3ADEXT 9 Extent Descriptions 135 (87) DS3PTRDS Reserved Figure 17. Offset 139 (8B) Data set Control Block -- Format 3 Bytes and Alignment Field Name Hex. Dig. Field Description. Contents, Meaning 0 (0) 4 (Key 03 identifier) A hexadecimal 03 in each byte. 4 (4) 40 DS3EXTNT Extent (in key) - four ten-byte fields indentical to the DS1EXT1 field in the format 1 DSCB. 44 (2C) 1 DS3FMTID 45 (2D) 135 (87) 90 • '. • 5 F3 Format identifier - Hex F3. DS3ADEXT Additional extent - nine ten-byte fields identical to the DS1EXT1 field in the format 1 DSCB. DS3PTRDS Reserved - contains binary zeros. c 136 OS System Control Blocks Data Set Control Block-Format 4 This data set control block (DSCB) describes the volume table of contents (VTOC) data set. It is always the first DSCB in the VTOC. Figure 18 shows the format of a format 4 DSCB. Descriptions of the fields follow the illustration. DSCB 137 DATA SET CONTROL BLOCK -- FORMAT 4 - 1 Padding Bytes 44 (2C) DS41DEMT Format Identifier 45 (2D) ~I' DS4HPCHR Highest Disk Address of Format 1 DSCB 50 (32) 52 (34) DS4DSREC No. of Available Format 0 DSCBs in VTOC DS4HCCHH CCHH of Next Alternate Track 56 (38) DS4NOATK No. of Alternate Tracks Available 58 (3A) 59 (3B) DS4VTOCI VTOC Indicators DS4NOEXT VTOC Constant Device Constants 60 (3C) 62 (3E) DS4DEVSZ No. of Logical Cylinders or No. of Tracks 66 (42) DS4DEVTK Device Track Length Reserved Continued 68 (44) DS4DEVI Constant for Keyed Block 72 (48) 69 (45) DS4DEVL Constant for Last Block DS4DEVTL Device Tolerance 70 (46) DS4DEVK Constant for no Key in Block 71 (47) DS4DEVFG No. of Directory Blocks Per Track 74 (4A) DS4DEVDT No. of DSCBs on a Track 75 (4B) DS4DEVDB No. of Directory Blocks Per Track 1- Reserve d .... r- 100 (64) DS4F6PTR Direct-Access Address of First Format 6 DSCB 105 (69) DS4VTOCE Extent Description of the VTOC 115 (73) ~L. Reserved T -"- 139 (8B)1 Figure 18,. Data Set Control Block -- Format 4 ( 138 OS System Control Blocks Offset o (0) 44 Bytes and Alignment Field Name DATA SET CONTROL BLOCK -- FORMAT 4 Hex. Dig. Field Description, Contents, Meaning 44 (Padding 04 Bytes) Hex 04 in each byte. (2C) 1 DS4IDFMT F4 Format identifier, Hex F4. (2D) • 5 DS4HPCHR Highest address previously used for a format 1 DSCB. The address is in the format CCHHR. 50 (32) •• 2 DS4DSREC Number of available format 0 DSCBs in the VTOC. 52 (34) 4 DS4HCCHH CCHH of next alternate track available. 56 (38) 2 DS4NOATK Number of alternate tracks available. 58 (3A) •• 1 DS4VTOCI VTOC Indicators. Either no format 5 DSCBs exist or they do not reflect the true status of the volume. (Reserved bits) 1 ••• .xxx xxxx 59 (3B) ••• 1 60 (3C) 2 DS4NOEXT 01 Hexadecimal constant '01' to indicate the VTOC is one extent. Reserved Device constants (DS4DEVxx) The following fields describe the device on which this volume was mounted when the VTOC was created. 62 (3E) •• 4 62 (3E) Bytes 1-2 Number of logical cylinders. A logical cylinder is the smallest collection of two or more tracks that can be processed by a set file mask CCW (hex IF). 64 (40) Bytes 3-4 Number of tracks per logical cylinder. 66 (42) •• 2 DS4DEVTK Device track length. Number of available bytes on a track exclusive of home address and record zero. 68 (44) 1 DS4DEVI Overhead bytes required for a keyed block that is not the last block on a track (see note). Note: Overhead bytes are the number of bytes required for gaps, check bits, and count field for each block. 69 (45) • 1 DS4DEVL Overhead bytes required for a keyed block that is the last block on a track (see preceding note). 70 (46) •• 1 DS4DEVK Overhead bytes to be subtracted from DS4DEVI or DS4DEVL if block has no key field. 71 (47) ••• 1 DS4DEVFG Flag byte. DS4DEVSZ xxxx xxx. ••• 1 Device size. (Reserved bits) A tolerance factor must be applied to all but the last block of the track. DSCB 139 DATA SET CONTROL BLOCK -- FORMAT 4 Offset Bytes and Alignment Field Field Description. Contents. Meaning 72 (48) 2 DS4DEVTL Device tolerance. Value which when divided by 512 is used to determine effective length of a block on a track. 74 (4A) •• 1 DS4DEVDT Number of full DSCBs that can be contained on one track (44 byte key plus 96 byte data length). 75 (4B) ••• 1 DS4DEVDB Number of full PDS directory blocks that can be contained on one track (8 byte key plus 256 byte data length) • 76 (4C) 24 100 (64) 5 DS4F6PTR Pointer to the first format 6 DSCB. This pointer has the form CCHHR. It contains binary zeros when not in use. 105 (69) • 10 DS4VTOCE VTOC extent. contents and meaning are the same as DS1EXTl in the format 1 DSCB. 115 (73) • • • 25 Reserved Reserved c 140 OS System Control Blocks Data Set Control Block-Format 5 This data set control block (DSCB) describes the amount of available space on the volume that can be allocated to a data set. Up to 26 available extents can be recorded in one format 5 DSCB. Additional extents are described in other format 5 DSCBs. The first format 5 DSCB follows the format 4 DSCB. Figure 19 shows the format of the format 5 DSCB. Descriptions of the fields follow the illustration. OSCB 141 DATA SET CONTROL BLOCK -- FORMAT 5 0(0) DS5KEYID Key ID 4 (4) DS5AVEXT An Avai lable Extent 9 (9) -"- -'"" DS5AVEXT 7 More Available Extents 44 (2C) DS5FMTlD Format Identifier -r 45 (2D) DS5MAVET 18 More Available Extents 135 (87) DS5PTRDS Direct-Access Address of Next Format 5 DSCS Figure 19. Offset 139 (8S) Data Set Control Block -- Format 5 Bytes and Alignment Field Name Hex. Dig. Field Description, Contents, Meaning o (0) 4 DS5KEYID 05 Key identification - Hex 05 in each byte. 4 (4) 5 DS5AVEXT Available extent, space available for allocation of a data set. 4 (4) Bytes 1-2 Relative track address of the first track in the extent. 6 (6) Bytes 3-4 Number of full cylinders in the extent. 8 (8) Byte 5 Number of tracks in the extent in addition to full cylinders. 9 (9) 44 • 35 DS5EXTAV Available extents. 7 five-byte fields identical in format to the DS5AVEXT field. (2C) 1 DS5FMTID Format identifier 45 (2D) • 90 DS5MAVET Available extents. 18 five-byte fields identical in format to the DS5AVEXT field. 135 (87) ••• 5 DS5PTRDS Pointer to next format 5 DSCB. This pointer has the form CCHHR. 142 OS System Control Blocks Hex F5. c Data Set Control Block-Format 6 This data set control block (OSCB) is used for shared cylinder allocation. It describes the extent of space (one or more contiguous cylinders) that are being shared by two or more data sets. Up to 26 extents can be described in one format 6 OSCB. Additional extents are described in other format 6 OSCBs. The format 6 OSCB is pointed to by the format 4 OSCB. Figure 20 shows the format of the format 6 DSCB. Descriptions of the fields follow the illustration. ) DSCB 143 DATA SET CONTROL BLOCK -- FORMAT 6 9 (0) DS6KEYID Key ID 4 (4) DS6AVEXT Address and Size of a Shared Extent 9 (9) DS6EXTAV Address and Size of Seven More Shared Extents _L.. 44 (2C) _L.. - 45 (2D) DS6FMTID Format Identifier DS6MAVET Address and Size of Eighteen More Shared Extents "135 (87) DS6PTRDS Direct-Address Address of Next Format 6 DSCB Figure 20. Offset 139 (8B) Data Set Control Block -- Format 6 Bytes and Alignment Field Name Hex. Dig. Field Description. Contents, Meaning 0 (0) 4 DS6KEYID 06 Key identification - Hex 06 in each byte. 4 (4) 5 DS6AVEXT Extent of space (one or more contiguous cylinders) that is being shared by one or more data sets. 4 (4) Bytes 1-2 Relative track address of the first cylinder. 6 (6) Bytes 3-4 Number of full cylinders being shared. 8 (8) Byte 5 Number of data sets sharing the extent. 9 (9) · 44 (2C) 1 45 (2D) · 135 (87) ·.. 35 90 5 DS6EXTAV Shared extents. 7 five-byte fields identical in format to DS6AVEXT. The fields are in relative track address sequence. DS6FMTID F6 Format identifier DS6MAVET Shared extents. 18 five-byte fields identical in format to DS6AVEXT. DS6PTRDS Pointer to next format 6 DSCB. This pointer has the form CCHHR. - Hex F6. ( 144 OS System Control Blocks Data Set Labels-Magnetic Tape The blocks of information that serve as labels for data sets residing on magnetic tape are the data set label 1 and the data set label 2. These blocks are 80 bytes long and are in EBCDIC characters in main storage and on nine-track tape, and in BCD characters on seven-track tape. I A set of a data set label 1 and a data set label 2, together with user labels (if used), is used to make up header labels, end-of-volume trailer labels, and end-ofdata-set trailer labels. Separate diagrams and descriptions are presented for these different formats: • Data Set Labell (FL1) • • Data Set Label 2 (FL2). DSL 145 c Data Set Label I-FLI Data set label 1 is 80 characters in length and describes the associated data set. This format is used for header labels, endof-volume trailer labels, and end-of-data set trailer labels. It is followed by data set label 2. All header labels, end-ofvolume trailer labels, and end-of-data set trailer labels must consist of both of these labels. In main storage these labels are recorded in EBCDIC. They are written in extended binary coded decimal interchange code (EBCDIC) on nine track tape units and in binary coded decimal (BCD) on seven track tape units. Figure 21 shows the format of data set label 1. Descriptions of the fields follow the illustration. DSL 147 DATA SET LABEL 1 -- FL1 0(0) 3 (3) FLlLABI Label ID FL1NO Label No. FLlID D00 t Se t ID :;:: 4 (4) ...,r- ...,r 21 (15) FLlFILSR Data Set Serial No. Continued Continued Continued Continued 27 (lB) FL 1VOLSQ Volume Sequence No. 31 (IF) FL 1FILSQ Data Set Sequence No. 35 (23) FL 1GNO Generation No. 39 (27) FL1VNG Version No. 41 (29) FL1CREDT Creation Date 47 (2F) FL 1EXPDT Expiration Date 53 (35) FL1FSEC Security 54 (36) FL1BLKCT Trailer Block Count ~h FL 1SY SC D System Code r60 (3C) ~ 73 (49) Reserved 79 (4F) Figure 21. Data Set Label 1 ( 148 OS System Control Blocks Offset o (0) 3 (3) 4 (4) 21 Bytes and Alignment Field Name DATA SET LABEL 1 -- FLl Hex. Dig. Field Description. Contents, Meaning FL1LABI Label identifier. HDR - header label. EOV - end-of-volume trailer label. EOF - end-of-data set trailer label. FL1NO Data set label number 17 FL1ID Data set identifier. (15) • 6 FL1FILSR Data set serial number. Same as the code that appears in the VOLSERNO field of the initial volume label of the first or only volume of the data set or multi-data set aggregate. 27 (lB) ••• 4 FL1VOLSQ Volume sequence number. Indicates the volume on which the data set is recorded in relation to the volume on which the data set begins. 31 (IF) ••• 4 FL1FILSQ Data set sequence number. Indicates the position of the data set relative to the first data set in a multi-data set aggregate. 35 (23) ••• 4 FL1GNO Generation number of the data set. 39 (27) • 2 FL1VNG version number of a generation of the data set. 41 (29) FL1CREDT Creation date. year and day - in format byyddd. 3 • 1 • 6 b yy ddd 47 (2F) ••• 6 FL1EXPDT 53 (35) • 1 FL1FSEC = 1. blank year (00-99) day (001-366) Expiration date. Expressed in the same format as creation date. FO Fl Data set security indicator. Data set is not security protected. Data set is security protected. 54 (36) •• 6 FL1BLKCT Unused in header labels - zero. In trailer labels, the number of blocks in the data set or on the current volume of a mUlti-volume data set. 6 (3C) 13 FL1SYSCD System code identifying the programming system. 73 (49) • 7 Reserved - must be recorded as blanks. DSL 149 ( Data Set Labe12-FL2 Data Set label 2 immediately follows data set label 1. It is 80 characters in length and contains information about the data set, in addition to that in data set label 1. Figure 22 shows the format of data set label 2. Descriptions of the fields follow the illustration. DSL 151 DATA SET LABEL 2 -- FL2 0(0) 4 (4) FL2LABI Label ID FL2RECFM Record Format 3 (3) 5 (5) FL2BLKL Block Length 10 (A) FL2LRECL Record Length 16 (10) FL2FILP Volume Switch FL2NO Label No. 15 (F) FL2DEN Density 17 (11) FL2JOBD Job ID 25 (19) FL2JSSP /(Slash) 26 (lA) FL2STEPD Step ID 34 (22) 36 (24) FL2CNTRL Printer Control 37 (25) -I- Reserved 38 (26) FL2TRTCH Recording Technique FL2BLKA Block Attribute 39 (27) .,JI-... Reserved 1 79 • Figure 22. (4F)J Data Set Label 2 ( 152 OS System Control Blocks DATA SET LABEL 2 -- FL2 Offset Bytes and Aligrunent Field Name Field Description, Contents, Meaning o (0) 3 FL2LABI Label identifier. HDR - Header label. EOV - End-of-volume trailer label. EOF - End-of-data set trailer label. 3 (3) ••• 1 FL2NO Data set label number = 2. 4 (4) 1 FL2RECFM Record F V U - 5 (5) • 5 FL2BLKL Block length. Depends on the record format. Form F - Block length Form V - Maximum block length Form U - Maximum block length 10 (A) •• 5 FL2LRECL Format F records: Record length. Format U records: Zero. Format V records Unspanned record format: Maximum record length. Spanned record format Records up to 32,756 bytes: Maximum record length. Records exceeding 32,756 bytes: 99999. 15 (F) ••• 1 FL2DEN Tape density. 2400 Series Magnetic Tape Devices. Field Value in EBCDIC 7-track 9-track o 200 bpi 1 556 bpi 2 800 bpi 800 3 1600 16 (10) 1 FL2FILP Data set position. Field Value in EBCDIC 1 Volume switch previously occurred o No volume switch has occurred 17 (11) 8 FL2JOBD Job Identification. 25 (19) · · 1 FL2JSSP Slash 26 (lA) FL2STEPD step identification. 34 (22) FL2TRTCH These characters denote the tape recording technique used to create this dataset (7-track tape only) • ·.8 ·.2 Cb Eb Tb ET format. Fixed length. Variable length. Undefined length. (/) . - Data conversion feature used. Even parity used. BCD to EBCDIC translation required. Even parity and BCD to EBCDIC translation required. bb - Odd parity and no translation required. DSL 153 DATA SET LABEL 2 -- FL2 Offset 36 (24) Bytes and Alignment 1 Field Name FL2CNTRL Field Description, Contents, Meaning Printer control This character denotes whether a printer carriage control set was used to create the data set and the type of carriage control specified. A - ASA control characters. M - Machine control characters .• b - Records do not contain control characters. 37 (25) • 1 38 (26) •• 1 39 (27) • • • 41 Reserved FL2BLKA Block attribute. B - Blocked records. S Spanned records. R Records are both blocked and spanned. b Records are neither blocked nor spanned. (b - blank) Reserved Must be recorded as blanks. ( 154 OS system Control Blocks Device Name Table The device name table (DNT) contains all of the device names that are in use. This table is a part of the job management initiator/terminator routine. The information in this table and the UCBs is used in allocation of devices as specified in DD cards. Figure 23 shows the format of the device name table. Descriptions of the fields follow the illustration. DNT 155 DEVICE NAME TABLE :-------------------------------------------------------------------------------l I o I~ _ (0) Number of Entries 3 (3) I 0 Device Entries l----oevyce--Entry-------------------------------------------------------------------------------------------------------------.. ---------------------------------------------------------- ll~ - 1 -r- Device Name r1 +8 Device Type +11 Device Entry Devi ce Entry Device Entry _______________________________________________________________________________ J Figure 23. Device Name Table ( 156 os System Control Blocks DEVICE NAME TABLE Offset Bytes and Alignment Field Description, Contents, Meaning Number of Entries. o (0) 4 The number of 12 byte entries in the table. one entry. Each device name has THE FOLLOWING 12 BYTE FIELD IS REPEATED FOR EACH DEVICE +0 8 Device name. A device name which is in one of three classes: specific, generic, or user assigned. The name is left justified and padded with blanks to the right. Specific name: IBM generated 3 character or 5 character (if the device is a 2321) name. The first byte indicates the channel, the second byte indicates the control unit, and the third byte indicates the device. If the device is a 2321, the fourth byte is a slash (/) and the fifth byte indicates the bin. Examples: 180 (tape) 190 (direct access) 193/5 (2311) Generic name: IBM generated name up to 8 characters in length. Examples: 2400 (2400 series 9-track Magnetic Tape Drive) 2311 (disk drive) User assigned name: User assigned name up to 8 characters in length. Examples: MAGTAPE +8 Device type. +8 4 Generic name: The contents of the field are the same as those of the UCBTYP field in the UCB. +8 2 Specific name, user assigned name: A digit one higher than the digit for the preceding specific or user assigned name. The first entry for a specific or user assigned name will contain a 1 in this field. • . 1 xxxxxx •• If one device is associated with the device name, these bits will be the same as bits 0-5 of the device class field (byte 3) of the UCBTYP field. If more than one device is associated with the name, these bits will indicate the result of ORing the device class field of the UCBTYP field for each device • •••• •• 00 Always zero. • • ~ 1 Zero DNT 157 c Event Control Block The event control block (ECB) is used for communication between various components of the control program, as well as between processing programs and the control program. An ECB is the subject of WAIT and POST macro instructions. Figure 24 shows the format of the event control block. A description of its fields follows the illustration. +1 Figure 24. Offset +0 Event Control Block Bytes and Alignment Field Name Hex. Dig. Field Description, Contents, Meaning Awaiting completion of an event: W - waiting for completion of an event. After completion of an event: C - The event has completed • completion code • 1 1 ••• • 1 •. • • xx xxxx One of the following completion codes will appear at the completion of a channel program: Access Methods Other Than BTAM Channel program has terminated without error. contents useful.) 41 Channel program has terminated with permanent error. (CSW contents useful.) 42 Channel program has terminated because a direct access extent address has been violated. (CSW contents do not apply.) 44 Channel program has been intercepted because of permanent error associated with device end for previous request. You may reissue the intercepted request. (CSW contents do not apply.) 48 Request element for channel program has been made available after it has been purged. (CSW contents do not apply.) 4F Error recovery routines have been entered because of direct access error but are unable to read home address or record o. (CSW contents do not apply.) Completed normally completed with an I/O error Enable command halted, or, I/O operation purged. Completed with an I/O error Enable command halted, or, I/O operation purged. 7F 41 48 41 48 +1 • 3 (CSW 7F Awaiting completion of an event: Request block address. After completion of the event: Zeroes, or remainder of completion code. ECB 159 ( Interruption Control Block The interruption control block (ICB) is created by the Open routines when chained channel-program scheduling has been specified. The lCB is used by the access method routines and is always pointed to by an lOB. Figure 25 shows the format of the lCB. Descriptions of the fields follow the illustration. lCB 161 INTERRUPTION CONTROL BLOCK 0(0) Link Address 4 (4) ECB 8 (8) Flag 1 9 (9) Flag 2 I/o flags 10 (A) I/o flags Sense 1 First Sense Byte 11 (B) Sense 2 Second Sense Byte 12 (C) ECB Address 16 (10) Flag 3 lOS error flags 17 (11) CSW Low-Order Bytes of Last CSW 24 (18) Channel Program Pointer Address of Channel Program to be Executed 28 (Ie) Increment Amount Block Count Constant 30 (IE) Indicators 31 (IF) Direct - Access Storage Devices 1 Seek Information No. of DEB Extent and Seek Address (This field is present only for direct-access storage devices) 132 (20) 39 (28) Channel Program Channel Program Figure 25. 1 -...... J Interruption Control Block ( 162 OS System Control Blocks INTERRUPTION CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning Link Address. o (0) 4 Address of the next ICB. first ICB. 4 (4) 4 Event control block. Shows status of an I/O operation. 8 (8) 1 Flag byte 1. 00 •• 01 •• 10 •• 11 •• •• 1. ••• 1 1 .•• .1 .• •.1. ••• 0 • . •1 The last ICB points to the No chaining (see note). Command chaining (see note). Data chaining (see note). Both command and data chaining (see note). Error routine in control • Device is to be repositioned • Cyclic redundancy check (CRC) needed - tape only. Exceptional condition. If this bit is on after control has been returned from the error routine, the error is considered permanent. lOB unreleated flag (i.e., nonsequential) • START • RESTART. Note: Chained channel-program scheduling does NOT depend on these bits to perform its chaining. 9 (9) . 1 Flag byte 2 • 1 ••• • 1 •• •• 1. ••• 1 xxx. ••• 1 10 (A) 11 (B) . 12 (C) 4 1 .. Halt I/O has been issued. Sense will not be performed until the device is free • lOB has been purged • Home address (RO) record is to be read • Internal I/O supervisor error correction flags. QSAM error recovery routine in control for a 2540 Punch with three buffers. First sense byte (device dependent). 1 Second sense byte (device dependent). Address of the ECB to be posted upon completion of an I/O event. ECB address. EXCP - Address of the ECB to be posted upon the completion of an I/O event. BSAM/BPAM - Address of the ECB in the DECB to be posted upon the completion of an I/O event. QSAM - Address of the ECB in the QSAM prefix to the lOB to be posted upon the completion of an I/O event. ICB 163 Offset Bytes and Alignment Field Name INTERRUPTION CONTROL BLOCK Hex. Dig. Field Description, Contents, Meaning Flag byte 3. 16 (10) Flags for I/O supervisor error routine (device dependent) • 7 CSW 17 (11) Low order seven bytes of the last CSW. status for this request. • 7 Shows channel Channel Program Pointer 24 (18) Address of the channel program to be executed. 4 Increment Amount Magnetic tape 28 (lC) Constant that is used to increment the block count. 2 Always zero for direct access. 30 (lE).. 2 30 (lE) •• 1 Indicators. 1. •.• • ••• • xxx xxxx Special volume full indicator signifying end-of-tape mark or reflective spot sensed along with a read or write erroro (Reserved Bits) Always zero • 31 (IF) ••• 1 Reserved 32 (20) 8 Seek Information This field is present for direct access devices only. 32 (20) Byte 1 The number of the DEB extent to be used for this request. The first extent is number zero. 33 (21) Bytes 2-8 The Seek address for this I/O request. 40 (28) Channel program. ( 164 OS System Control Blocks Input/Output Block The input/output block (IOB) is the communication medium between a routine that requests an I/O operation and the I/O supervisor. All the information required by the I/O supervisor to execute an I/O operation is contained in the IOB, or is pointed to by the IOB. Figure 26 shows the format of the IOB. Descriptions of the fields follow the illustration. The IOB format falls into three segments whose use varies mainly by access method: Prefix -• GAM. QISAM. • BSAM. QSAM, BPAM • BSAM. QSAM, BPAM Normal scheduling. Chained scheduling. standard Fields • Displacements 0-31 (decimal), 0-lF (hexadecimal) • Extension • • • • • • • BTAM. GAM. Direct-access storage devices. BSAM. QSAM. BPAM. QISAM, Scan Mode. BISAM. BDAM. The following illustrates the relationship of these segments. Prefix Segment 0(0) Standard Fields Segment 32 (20) Extension Segment IOB 165 INPUT/OUTPUT BLOCK PREFIX ----G-A-M-;-a-isA-M---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1-4 (-41 Event Control Block -1 (-1) QSAM, BSAM, BPAM - Normal Scheduling -8 (-8) -7 (-7) I/o Flags Address of Next lOB -4 (-4) Event Control Block -1 (-1) QSAM, BSAM - Chained Scheduling -16 (-10) FLAG 1 Indicators -15 (-F) I/o -14 (-E) INNOP Offset to Last I/O for Input Reserved -13 (-D) OUTNOP Offset to Last I/o for Output -12 (-C) Event Control Block -8 (-8) FIRSnCB Address of First ICB -4 (-4) Last NOP Address -1 (-1) Standard Fields 0(0) IOBFLAG1 I/o Flags 1 (1) 4 (4) 10BECBCC Completion Code 5 (5) 8 (8) IOBFLAG3 Error Flags IOBFLAG2 I/o Flags 2 (2) 3 (3) 10SENSO First Sense Byte IOBSENS1 Second Sense Byte 10BECBPT Address of ECB 9 (9) I/o 10BCSW Seven Low-Order Bytes of Last CSW 16 (10) 10BSIOCC SIO Condition Code 20 (14) 17 (11) 10BSTART Address of Channel Program 21 (15) 10BDCBPT Address of DC B Reserved 24 (18) 10BRESTR PURGE Chain/CCHH/Command, Channel Program 28 (1C) 10BINCAM (use vari es) -Figure 26. 30 (lC) 10BERRCT No. of Error Retries 31 (1F, Input/Output Block (Part 1 of 3) c 166 OS System Control Blocks INPUT/OUTPUT BLOCK Extension r---STAM---------------------------------------------------------------------------------------------------------------------------------------.---------------------------------------------.----~ 32 (20) 10BUCBX UCB Index 33 (21) 10BWORK Error Routine and ONL TT Routine Work Area _~O (28) 1. 10BERCCW Error Routine CCW (30) -L.. I I 10BERINF Error Routine Data L(40) ""'- 10BCPA Channel Programs I ""'- ""'- J GAM 32 (20) 10BUCBX UCB Index 36 (24) 33 (21) Reserved 37 (25) 10BNXTPT Address of Next Available lOB Status Indicators ..J ... 40 (28) 10BCCW List of CCWs T 132 -a.. 71 (47)} 10BSEEK No_ of DEB Extent and Seek Address (This field may be present only for direct-access storage devices) (20) 1 39 (27) BSAM, QSAM, BPAM L ""'- I 1 ""'""'- Channel Program J Addi tiona I Search Addresses (This field may be present only for direct-access storage devices) Continued Figure 26. Input/Output Block (Part 2 of 3) lOB 167 INPUT/OUTPUT BLOCK Extension (Continued) r---os-iAM----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------, 40 (28) W1IEXTEN,W10EXTEN Appendage Codes 41 (29) BISAM 40 (28) 10BCCWAD Address of First CCW 44 (2C) 10BINDCT Queue Indicators 48 (30) 10BCOUNT Write Check Count 45 (2D) 10BUNSOR Reason Queue Unscheduled 46 (2E) 49 (31) 52 (34) 10BAPP Appendage Codes 47 (2F) 10BASYN Asynchronous Code 10BCHAD Forward Chain Address 10BBCHAD Backward Chain Address 55 (37) BDAM 40 (28) 44 (2C) 10BDBYTR No. of Unused Track Bytes 10BDAVLI Availability Indicator 48 (30) 45 (2D) 50 (32) 10BDSTAT Status of Request IOBDCPND Address of Channel Program End 10BDBYTN No. of Bytes Per Block 60 (3C) 58 (3A) Reserved 10BDQPTR Address of Next lOB -'... 64 (40) -L... Reserved L(481 10BDNCRF Count Field for Next Block t(SOI Channel Program I 1 T T Figure 26. 168 10BDIOBS Size of lOB 10BDPLAD Address of Next lOB in Pool 10BDTYPE Type of I/o and Options 52 (34) 56 (38) 42 (2A) Input/Output Block (Part 3 of 3) OS System Control Blocks INPUT/OUTPUT BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning PREFIXES GAM, QISAM PREFIX -4 (-4) 4 GAM: Event control block that is within first lOB only. QISAM: Event control block used to indicate status of an I/O event. BSAM, QSAM, BPAM -- NORMAL SCHEDULING PREFIX -8 (-8) Flag byte. 1 1 ••• • 1 •• •• 1. .•. 1 1 •.. • xx. ••• 1 PRTOV has occurred. A WRITE operation is in process • A READ operation is in process • Update flag. Set on together with bit 1 of this byte to show that the block is to be updated. Can only occur if the OPEN parameter is UPDAT. lOB being used for backspace, control, or note/point operation. (Reserved bits) • This is the first lOB • -7 (-7) • 3 Address of the next lOB associated with one particular DCB. The lOBs are chained in sequential order. -4 (-4) 4 An ECB used by QSAM to indicate the status of the I/O event. BSAM, QSAM, BPAM -- CHAINED SCHEDULING PREFIX -16 (-10) 1 FLAGl xxxx x ••• .1 •• • • 1. ••• 1 .1 '. . 1 -15 (-F) -14 (-E) -13 (-D) ...1 -12 (-C) 1 -8 (-8) 4 -4 (-4) 4 I/O Indicators. (Reserved bits) Error has been processed once by abnormal-end appendage routine. Restart channel • Set when a program-controlled interruption (PCI) occurs. Reserved INNOP Offset of the last I/O instruction for input operation (NOP CCW) from the origin of the ICB. OUTNOP Offset of the last I/O instruction for an output operation (NOP CCW) from the origin of the ICB. An ECB used by BSAM or QSAM. I/O operation. FIRSTICB Shows the status of the Address of the first interrupt control block (ICB) on the ICB queue. Address of the NOP instruction at the end of the queue. ) lOB 169 INPUT/OUTPUT BLOCK Offset Bytes and Alignment Field Name Field Description. Contents. Meaning STANDARD FIELDS o (0) 1 IOBFLAGl 00 •• 01 •• 10 •• 11 •• •• 1. •••1 1 •.• .1 .. •• 1. ••• 0 ••• 1 1 (1) • IOBFLAG2 1 1. '•. • 1 •• •• 1. .•. 1 xxx. • '•• 1 2 (2) 1 3 (3) • 4 (4) 1 5 (5) • 8 (8) 1 9 (9) • 3 7 1 Flag byte 1 No chaining. Command chaining. Data chaining. Both command and data chaining. Error routine in control • Device is to be repositioned • Cyclic redundancy check (CRC) needed - tape only. Exceptional condition. After the error routine returns and this bit is on. the error is considered permanent • lOB unrelated flag (i.e., nonsequential) • START RESTART Flag byte 2 Halt I/O has been issued. Sense will not be performed until the device is free • lOB has been purged • Home address (RO) record is to be read • Internal I/O supervisor error correction flags. QSAM -- error recovery in control for a 2540 Punch with three buffers. BTAM -- RESETPL macro instruction was used. IOBSENSO First sense byte (device dependent). IOBSENSl Second sense byte (device dependent). IOBECBCC completion code for an I/O event. This code will appear in the first byte of an ECB. (For specific codes see ECB.) IOBECBPT EXCP - Address of the ECB to be posted upon the completion of an I/O event. BSAM/BPAM - Address of the ECB in the DECB to be posted upon the completion of an I/O event. QSAM - Address of the ECB in the QSAM prefix to the lOB to be posted upon the completion of an I/O event. IOBFLAG3 I/O supervisor error routine flag byte (device dependent) • IOBCSW Low order seven bytes of the last csw that reflects the status for this request. ( 170 OS System Control Blocks INPUT/OUTPUT BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning STANDARD FIELDS • 89 (S9) '. 1 JFCBBIAR" x. '••• x •• 0.,• • • 0.,. 0 •• ,• • 1 •• JFCBFTEK, JFCBFALN Code Access methods other than QTAM Buffer pool location, coded in the DD statement 0, Hierarchy 0 main storage. none 1 Hierarchy 1 main storage. .x.x x ••• • 1 •• .•• 1 1 ••• S E D (Reserved bit) • x •• '•• xx • • 10 •• 01 ) 90 (SA) ... 2 JFCBUFL Buffering technique: Simple buffering • Exchange buffering • Dynamic buffering. D F Buffer alignment: Doubleword boundary • Fullword nota doubleword boundary • Buffer length JFCB 181 JOB FILE CONTROL BLOCK Offset 92 (SC) Bytes and Alignment 1 Field Name JFCEROPT 1 •• '. .1 •• •• 1. ••• x xxxx Field Description, Contents, Meaning Error option. Disposition of permanent errors if user returns from a synchronous error exit. (QSAM) Accept Skip Abnormal end of task (Reserved bits) Device Characteristics Field 93 (SD) The content of this one-byte field depends upon the device in use. MAGNETIC TAPE 93 (SD) • 1 JFCTRTCH 0010 0011 0001 0010 0011 1011 0011 1011 Tape recording technique for seven track tape. Code Even parity. E T BCD/EBCDIC translation. C Data conversion. ET Even parity and translation. DIRECT-ACCESS STORAGE 93 (SD) • 1 JFCKEYLE Direct access key length. CARD READER" CARD PUNCH 93 (SD) '. 1 JFCMODE 1000 0100 JFCSTACK 0001 0010 Mode of operation. Code C Column binary mode. E EBCDIC mode. Stacker Selection. Code --1- Stacker 1 2 Stacker 2 PRINTER 93 (SD) • 1 JFCPRTSP 0000 0000 0001 0001 0001 1001 0001 100i Normal printer spacing. Code - 0 - No spacing,. 1 Space one line,. 2 Space two lines. 3 Space three lines. PAPER TAPE 93 (SD) • 1 JFCCODE 1000 0100 0010 0001 0000 0000 0000 0000 0000 0000 0000 1000 0100 0010 Conversion code. Code N No conversion. IBM BCD. I F Friden. B Burroughs. C National Cash Register. A ASCII (8-track). T Teletype. End of Device Characteristics Field. ( 182 OS System Control Blocks JOB FILE CONTROL BLOCK Offset 94 (5E) Bytes and Alignment •• 1 Field Name JFCDEN Field Description, Contents, Meaning Tape density. 2400 series magnetic tape units .. Code 7-track 0000 0100 1000 1100 95 (SF) ••• 3 96 (60) 2 98 (62) 98 (62) 0011 0011 0011 0011 JFCLIMCT . 1 1. '... . 1 ... •• 1. ••• x xx •• •• 1 .. .•. 1 99 (63) .. • • 1 (64) 1 JFCRECFM 10 ... 01 ... 11 •• . . 1 .. .•. 1 1 .... .. 10. • 01. • 00. .... 0 101 101 (65) (65) 556 bpi 800 bpi 3 800 bpi 1600 bpi BDAM: Search limit. .. 1 .. 1 JFCOPTCD 1 •.. .1 .. ... 1. ••• x Data set organization being used. Code IS Indexed sequential organization. PS Physical sequential organization • DA Direct organization • (Reserved bits) PO Partitioned organization • U UDnlovable - the data contains location dependent information .. GS 0 .. '... .xxx xxxx 100 1 2 9-track Data set opened for MOD: If automatic step restart was requested - Track balance existing when the data set was first opened during the original execution of the current step. JFCDSORG .. - 0 - 200 bpi xx .. 1 .. X .. Graphics organization .. (Reserved bits) Record format. Code F Fixed. V Variable. U Undefined .. T Track overflow. B Blocked: may not occur with undefined (U) .. S Fixed length record format: Standard blocks no truncated blocks or unfilled tracks are embedded in the set. Variable length record format: Spanned records .. A ASA control character • M Machine code control character .. No control character .. Always zero .. Option codes. QSAM, BSAM, BPAM Code W Write validity check. U Allow a data check caused by an invalid character (1403 printer with UCS feature.) C Chained scheduling using the Program Controlled Interruption .. (Reserved bits) z Magnetic Tape Devices: Used reduced error recovery procedure. JFCB 183 JOB FILE CONTROL BLOCK Offset 101 (65) Bytes and Alignment • 1 Field Name 1 •• '. .x. I. ,.x. '. • .• 1. • '•• 1 1 ••• • • 1 .• •.. . 1 Field Description, Contents, Meaning BISAM, QISAM Code ---W- Write validity check. (Reserved bits) M Master Indexes. I Independent overflow area. Y Cylinder overflow area. L Delete option • R Reorganization criteria .• BDAM 101 (65) • 1 --w- Write 1 .••• • 1 •• • ,.1. .• • • 1 1 ••• E F A .xx. •.. . 1 102 (66) •• 104 (68) 106 107 2 R validity check. Track overflow • Extended search. Feedback • Actual addressing,. (Reserved bits) Relative block addressing • JFCBLI directory entry. Figure 30A shows the general format of an entry in a POS directory. Following the illustration is a general description of the fields of an entry. POS 197 1 10(0) Member or Alias Name -r- -~ 8 (8) Relative Address of Named Member Indicators :.: 12 (C) User Data T Figure 30A. T PDS Directory Entry -- General Format PDS DIRECTORY ENTRY Offset o (0) Bytes and Alignment 8 Field Description, Contents, Meaning Member name of alias name. TTR 8 (8) 3 TTR of the first block of the named member. c 11 (B) ••• 1 1. • • • xx. Indicators. Name is an alias,• Number of TTR' s in the user data field. A maximum of three is allowed • • ,•• x xxxx Length of the user data field in half words. User Data 12 (C) n variable user data as provided as input to the STOW macro instruction. Up to three pointers to locations within the member may be provided. The pointers must be four bytes long and must appear at the beginning of the user data field. Their format is as follows: TT - 2 bytes - Relative track from the beginning of the data set. R - 1 byte - Block number on that track. N - 1 byte - If the TTR points to a note list, this byte indicates the number of entries in the note list. If the TTR does not point to a note list, this byte contains zeros. The remaining bytes in the user data area are optional in their format and use. 198 OS System Control Blocks Partitioned Data Set Directory Entry-Format 1 This format appears in the partitioned data set (POS) directory and is the format produced by linkage editor for a load module. Figure 30B shows the format of an entry in a FOS directory for a load module. The difference between format 1 and format 2 of linkage editor POS directory entries lies in two fields inserted into format 1 at offsets +11 and +12 (decimal) by the BLOL routine when it places the entry into a BLDL list. POS 199 PDS DIRECTORY ENTRY A II Load Modu les 10(0) -.... 1 ' Member of Alias Name 8 (8) .... 11 (B) Re lative Address of First Block (TTR- P) Indicators 12 (C) 15 (F) Relative Address of First Block of Text (TTR-T) Zeros 16 (l0) 19 (13) Relative Address of Note List or Scat/Trans Table 20 (l4) No. of List Entries 22 (l6) Module Attributes Main Storage Needed for Module 25 (19) Continued 27 (lB) Length of First Text Block Entry Point Address 30 (lE) Continued First Text Block Origin Continued 32 (20) 33 (21) 35 (23) Scatter List Size 37 (25) Continued Translation Table Size 39 (27) ID of ESD for First Text Block Control Section ID of ESD Continued 40 (28) Load Modules With Alias Names and RENT or REUS Attributes 33 (21) Entry Point for Member Name 136 (24) -L. T Load Modules - Scatter, With Alias Names and RENT or REUS Attributes Member Name of a Load Module 43 (2B) T 40 (28) Entry Point for Member Name 144 T (2C) Member Name of a Load Module Figure 30B. 200 51 (33)T PDS Directory Entry -- Format 1 OS System Control Blocks PDS DIRECTORY ENTRY Offset Bytes and Aligrunent Field Description, Contents, Meaning standard Field o (0) 8 Load module member name or alias name .. 8 (8) 3 TTR of the first block of the named member (load module). Indicators 11 (B) ••• 1 Bit State Meaning Name is an alias in the first field. 1-2 (variable) Number of TTRs in the user data field. 3-7 (variable) Length of user data field in half words. o -----1 User Data Field TTR-T 12 (C) 3 15 (F) ••• TTR of the first block of text .. 1 Zeros. TTR-N/S 16 (10) 3 TTR of the Note List or Scatter/Translation Table. Used for modules in scatter load format or overlay structure only. NL 19 (13) ... 20 (14) 2 1 The number of entries in the note list for modules in overlay structure; otherwise zero. Attributes Byte 1 1 .•. • 1 •• •• 1. ••. 1 1 ••• • 1 .. •• 1. •..1 ••• 0 Reenterable .. Reusable .. In overlay structure • Module to be tested - TESTRAN • Only loadable. Scatter format • Executable .. Module contains no RLD items and only one block of text • Module contains multiple records with at least one block of text .. Byte 2 1. '.. 0 ••• • 1. '. • • 0. •• 1 .. .... 1 1 .... • 1 •. .• 1. • • •1 Module can be processed only by F level of linkage editor. Module can be processed by all levels of linkage editor. Linkage editor assigned origin of first block of text is zero • Linkage editor assigned origin of first block of text is not zero .. Entry point assigned by linkage editor is zero • Module contains no RLD items • Module cannot be reprocessed by linkage editor .. Module contains TESTRAN symbol cards • Module created by linkage editor F • Refreshable module .. PDS 201 PDS DIRECTORY ENTRY Offset Bytes and Alignment Field Description, Contents, Meaning User Data Field (Continued) Main Storage 22 (16) •• 3 Total contiguous main storage requirement of module. First Text Block Length 25 (19) • 2 Length of the first block of text. EP Address 27 (lB) _ _ • 3 Entry point address associated with member name or with alias name if the alias indicator is on. First Text Block Origin 30 (lE) •• 3 Linkage editor assigned origin of the first block of text. LOAD MODULE -- SCATTER Scatter List Size 33 (21) • 2 Number of bytes in the scatter list. Transl-Table Size 35 (23) ••• 2 Number of bytes in the translation table. ESDID-T 37 (25) _ 2 Identification of the ESD item (ESDID) of the control section to which the first block of text belongs. ESDID-CSECT 39 (27) ••• 2 Identification of the ESD item (ESDID) of the control section containing the entry point. LOAD MODULE -- ALIAS NAME AND RENT OR REUS ATTRIBUTE EP-Member Name 41 (29) • 3 The entry point associated with the member name when the first field is an alias name and the load module has reenterable or reusable attributes. Member Name 44 (2C) 8 The member name of the load module when the first field is an alias name and the load module has reenterable or reusable attributes. c 202 OS System Control Blocks Partitioned Data Set Directory EntryFormat 2 This format is received upon issuance of a BLDL macro instruction where the specified members are load modules produced by linkage editor. The user data field for a load module is described here. Figure 30e shows the format of PDS directory entries for linkage editor load modules in a BLDL list. Descriptions of the fields follow the illustration. The difference between format 2 and format 1 of linkage editor PDS directory entries lies in the concatenation number and library flag fields inserted in format 2 by the BLDL routine at offsets +11 and +12 (decimal). PDS 203 PDS DIRECTORY ENTRY All Load Modules 1 10(0) ~,... ~ Module Member Name or Alias 8 (8) ... 11 (B) Concatenation No. Relative Address of First Block 12 (C) 13 (D) 14 (E) Type of Library Indicators Relative Address of First Text Block 17 (1 I) Continued 18 (12) Relative Address of Note List or Scat/Trans Table Zeros 21 (15) No. of Note List Entries Continued 22 (16) Module Attributes 27 (1 B) 24 (18) Main Storage Needed for Module Length of First Text Block 29 (ID) Continued Entry-Point Address 32 (20) First Text Block Origin 34 (22) --------------------------- ... ------------------------------------- ... -------------------------------------------------------------------------------------------------------------------------------------, Load Module - Scatter 35 (23) Sea tter Li st Size Continued Continued 37 (25) Translation Table Size 39 (27) ID of ESD for First Text Control Section 41 (29) ID of ESD for Entry-Point Control Section Load Modules With Alios Names and RENT or REUS Attributes 35 (23) Entry-Point for Member Name 38(26) Continued Load Module Member Name 45 (2D) Load Modules -Scatter, With Alios Names and RENT or REUS Attributes 43 (2B) Entry-Point for Member Name 43(2B) Continued Load Module Member Name 53(35)1 Figure 30C. 204 PDS Directory Entry -- Format 2 OS System Control Blocks PDS DIRECTORY ENTRY Offset Bytes and Alignment Field Description, Contents, Meaning Standard Field 0 ( 0) 8 Name Load module member name or alias name. 8 (8) 3 TTR-P TTR of the f-irst block of the named member (load module). 11 (B) ... 12 (C) 1 13 (D) • 1 1 Concatenation number of the data set. Library This byte is normally zeros. If the DCB operand in the BLDL macro instruction was specified as zero, this byte will contain a 1 if the name was found in the link library, and a 2 if the name was found in the job library. Indicators Bit Setting Meaning o 1 Name is an alias in the first field. 1-2 (variable) Number of TTRs in the user data field. 3-7 (variable) Length of user data field in half words. User Data Field TTR-T 14 (E) 17 (11) 3 TTR of the first block of text. • 1 Zeros. TTR-N/S 18 (12) •• 3 TTR of the Note List or Scatter/Translation Table. Used for modules in scatter load format or overlay structure only. NL 21 (15) · 22 (16) ·. The number of entries in the note list for modules in overlay structure. 1 Attributes 2 Byte 1 1. '•• • 1 •• • .1,• •• ,.1 1,••• • 1 •• •• 1. ••• 1 ••• 0 Reenterable. Reusable • In overlay structure. Module to be tested - TESTRAN. Only loadable. Scatter format • Executable. Module contains no RLD items and only one block of text • Module contains multiple records with at least one block of text • Byte 2 1 ••• 0,•• '. ,.1 •• ,.0 •• • ,.1. ••• 1 1 ••• • 1,•• •• 1. '••• 1 Module can be processed only by F level of linkage editor. Module can be processed by all levels of linkage editor. Linkage editor assigned origin of first block of text is zero. Linkage editor assigned origin of first block of text is not zero. Entry point assigned by linkage editor is zero. Module contains no RLD items • Module cannot be reprocessed by linkage editor. Module contains TESTRAN symbol cards • Module created by linkage editor F • Refreshable module. PDS 205 PDS DIRECTORY ENTRY Offset Bytes and Alignment Field Description, Contents, Meaning User Data Field (Continued) Ma in storage 25 (19) • 2 Total contiguous main storage requirement of module. First Text Block Length 27 (lB) ••• 2 Length of the first block of text. EP Address 29 (lD) • 3 Entry point address associated with member name or with alias name if the alias indicator is on. First Text Block Origin 32 (20) 3 Linkage editor assigned origin of the first block of text. LOAD MODULE -- SCATTER scatter List Size 35 (23) ••• 2 Number of bytes in the scatter list. Transl-Table Size 37 (25) • 2 Number of bytes in the translation table. ESDID-T 39 (27) ••• 2 Identification of the ESD item (ESDID) of the control section to which the first block of text belongs .• ESDID-CSECT 41 (29) • 2 Identification of the ESD item (ESDID) of the control section containing the entry point. LOAD MODULE -- ALIAS NAME AND RENT OF REUS ATTRIBUTE EP-Member Name 43 (2B) ••• 3 The entry point associated with the member name when the first field is an alias name and the load module has reenterable or reusable attributes. Member Name 46 (2E) •• 8 The member name of the load module when the first field is an alias name and the load module has reenterable or reusable attributes. ( 206 os System Control Blocks Request Blocks Request blocks are used by the supervisor for maintaining information concerning programs and routines (logically distinct sections of code>. Other components of the control program may create request blocks and/or refer to information in them. The various request blocks are shown and described separately as follows: • PCP, MFT Configuration -IRB, LRB, LPRB, PRB, SIRB, SVRB: Figure 3iA and following text • MVT Configuration -- IRB: Figure 3iB and following text PRB: Figure 3iC and following text SIRB: Figure 3iD and following text SVRB -- Resident SVC Routines: Figure 3iE and following text Transient SVC Routines: Figure 3iF and following text RB 207 c Request Block-PCP, MFT Configurations Request blocks used by the PCP and MFT configurations of System/360 Operating System are described and illustrated here. Figure 31A shows the different formats; field descriptions follow the illustration,. RB -- PCP, MFT 209 REQUEST BLOCK -- PCP, MFT LPRB LRB -8 (-8) XRBSUC Load List Pointer to Previous RB -4 (-4) XRBPRE Load List Pointer to Next RB IRB PRB, SIRB SVRB ~--~---------~-------~------------------------------------------------------~-l I ,- ! 10 (0) 1 : XRBNM Program Name 8 (8) XRBSZ 12 (C) XRBUSE Use Count 10 (A) 13 (D) End of LRB -... XSTAB Flag Bytes XRBEP Entry-Point Address -----------------------------._----------------------------------------------------~--- 116(10) -r"" .. --- ,_.--------------------------- ------------------------_.-.--.-._----------._------------------------ 1 XRBPSW Save Area for PSW -I'" , 24 (18) 28 (1C) XRBQ XRBWT Wait Count 29 (10) XRBLNK Address of Previous RB or TCB , End of LPRB ---1------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ~-~~Q-~-fR~------------------------------------------- _________ ._._. ___ . ___ ._._ 1 1 ::::::32 (20) ~ _~ SYNC macro instruction requested,• XCTL macro instruction requested • Load macro instruction requested • • 3 RBCDE Address to contents directory entry for the modules that this request block is associated with. (10) 8 RBOPSW User's old PSW. 24 (18) 1 25 (19) • 3 RBPGMQ Address of a request block indicating a request to use the same serially reusable program.. 28 (le) 1 RBWCF Number of requests waiting (wait count). 29 (lD). 3 RBLINK Address of next request block, or Address of the TCB, when this is the first request block. 32 (20) 64 RB GR SAVE General register save area used by the supervisor: register sequence 0 to 15. 96 (60) 48 RBEXSAVE Extended save area for SVC routine. Zeros. SVRB -- MVT 233 ( Supervisor Request Block-MVTTransient SVC Routines This supervisor request block (SVRB) is used by the supervisor to hold information for type 3 or 4 (transient) svc routines. Figure 31F shows its format used in MVT; field descriptions follow the illustration. SVRB -- MVT 235 SUPERVISOR REQUEST BLOCK -- MVT -- TRANSIENT SVC ROUTINES 0(0) 4 (4) 8 (8) 2 (2) RBTABNO Displ for TACT Entry RBRTLNTH SVC Routine Length RBABOPSW 4 Low Order Bytes of Routine Name or Right-Half of User's Old PSW RBWCSA Wait-Count Save-Area 9 (9) RBSIZE Size of This RB 12 (C) 10 (A) RBSTAB Status and Attribute Bits RBSVTQN Address of Next RB on Transient User Queue _1,..16 (10) RBOPSW Old PSW -~ 24 (18) RBTAWCSA Wait Count Overlay Save Area 25 (19) 28 (1C) 29 (1C) RBWCF Wait Count -,-, -r- RBSVTTR TTR for SVC Routine RBLINK Address of Next RB or TCB -L.. .,.JL.,. :::::32 (20) RBGRSAVE General Register Save Area ......., ---- I :::::96 (60) ---- ......., I RBEXSAVE Extended Save Area for SVC Routines ......., ......., T 143 (8F) Figure 31F. ~ ......., ---- J Supervisor Request Block -- MVT -- Transient SVC Routines ( 236 OS system Control Blocks Offset SUPERVISOR REQUEST BLOCK -- MVT TRANSIENT SVC ROUTINE Bytes and Field Alignment Name Field Description, Contents, Meaning o (0) 2 RBTABNO Displacement from beginning of transient area control table (TACT) to entry for module represented by this SVRB. 2 (2) .... 2 RBRTLNTH Length of SVC routine in bytes. 4 (4) 4 RBABOPSW After execution of transient a.rea handler routine: Four low-order bytes of name of requested routine. After execution of ABTERM routine: PSW .. Right-half of old 8 (8) 1 RBWCSA Number of requests waiting at time of termination (wait-count save-area) .. 9 (0) .. 1 RBSIZE Size of request block in doublewords. 10 (A) •• RBSTAB Status and attribute bits. 2 Byte 1 00 •• 01 •• 10 .... 11 •• •.• x. X .. xx ..... • 1 .1 •.• Program request block (PRfr). Interruption request block (IRB) .. System interruption reques~ block (SIRB). Supervisor request block (SVRB) .. (Reserved bits) SVRB for transient SVC routines • A checkpoint may be taken in a user exit from this SVC routine. Byte 2 1 ••• • 1 •• •.• xx 00 •• 01 •• 11 •• •• 1. '••• 0 .••. 1 ) RBLINK field points to TCB. Program is active (applies to IRB or SIRB) • (Reserved bits) Request queue element is not to be returned. IRB has queue elements for asynchronously executed routines that are RQEs .. IRB has queue elements for asynchronously executed routines that are IQEs,. Request block storage can be freed at exit • Wait for a single event or all of a number of events. Wait for a number of events that is less than the total number of events waiting '. 12 (C) 4 RBSVTQN Address of next request block on queue of transient routines. 16 (10) 8 RBOPSW User's old PSW. 24 (18) 1 RBTAWCSA Save area for number of requests field used if transient routine is overlaid. 25 (19) • 3 RBSVTTR Relative direct access device address in the format of TTR for the SVC routine. 28 (lC) 1 RBWCF Number of requests waiting (wait count). 29 (lD) • 3 RBLINK Address of the next request block, or Address of the TCB, when this is the first request block. 32 (20) 64 RBGRSAVE General register save area used by the supervisor; register sequence 0 to 15 .. 96 (60) RBEXSAVE Extended save area for SVC routines. SVRB -- MVT 231 ( Task Control Block The task control block (TCB) serves as a repository for information and pointers associated with the task in progress. Various components of the control program place information in the TCB, and obtain information (or its location) by reference to it. Figure 32 shows the format of the TCB. Descriptions of the fields follow the illustration. » TCB 239 TASK CONTROL BLOCK 1 -.....-32 (-20) 0(0) ~ .... TCBRBP Address of RB 4 (4) TCBPIE Address of Program Interrupt Element 8 (8) TCBDEB Address of DEB Queue 12 (C) TCBTIO Address of Task I/o Table 16 (10) TCBCMP Task Completion Code 20 (14) TCBTRN Flag, Address of Control Core Table (TESTRAN) 24 (18) TCBNROC MVT: Roll-Out Eligibility 28 (1C) 1 TCBFRS Floating - Point Register Save Area "'11"" TCBPKE Protection Key 25 (19) TCBMSS PCP, MFT: Address of Boundary Box MVT: Address of Last SPQE 29 (18) TCBFLGS Task End, Miscellaneous, and Dispatchability Flags (PCP and MFT use differs from MVT use) 34 (22) TCBLMP PCP, MFT: Enqueue Count MVT: Limit Priority 35 (23) TCBDSP Dispatching Priority TCBLLS PCR, MFT: Address of Last RB for Program Loaded by LOAD MVT: Address of Load List Element for Program Loaded by LOAD 36 (24) 40 (28) TCBJLB Address of JOBLIB DCB 44(2C) PCP, MFT: Reserved MVT: TCBJ PQ - (Job Step TCB) Address of CDE for JPA -::::48 (30) ...... ... TCBGRS General Register Save Area 112 (70) PCP ,MFT: TCBIDF - TCB Identifier MVT: TCBQE L- Enqueue Count -Figure 32 .. 113 (71) TCBFSA Address of First Program Save Area Task control Block (Part 1 of 2) ( 240 OS System Control Blocks TASK CONTROL BLOCK 116 (74) TCBTCB Address of Next Lower Priority TCB 120 (78) TCBTME Address of Timer Element 124 (7C) PCP: Reserved MFT: TCBPIB, Partition Type Address of PIB MVT: TCBJSTCB-Address of 1st TCB for Job Step 128 (80) PCP, MFT: Reserved(a) MVT: TCBNTC - Address of Previous TCB on Subtask Queue 132 (84) PCP, MFT: Reserved(a) MVT: TCBOTC - Address of Originating TCB 136 (88) PCP, MFT: Reserved(a) MVT: TCBLTC - Address of Last TCB on Subtask Queue 140 (8C) PCP, MFT: Reserved(a) MVT: TCBIQE - Address of IQE for ETXR Routine 144 (90) PCP, MFT: Reserved(a) MVT: TCBECB - Address of ECB Posted on Task Completion 148 (94) PCP, MFT, MVT: Reserved (a) 152 (98) PCP, MFT: Reserved (a) MVT: TCBPQE - Address of Region Dummy PQE - 8 156 (9C) PCP, MFT: Reserved(a) MVT: TCBAQE - Address of Allocated Queue Element 160 (AO) TCBNSTAE STAE Flags Address of Current STAE Control Block 164 (A4) PCP, MVT: Reserved MFT: TCBTCT - CPU Time 168 (A8) TCBUSER User Field 171 (AB) (a) - Bytes 128-159 are overlayed by other blocks in PCP and MFT. • Figure 32 .. Task Control Block (Part 2 of 2) ) TCB 241 Offset -32 (-20) Bytes and Alignment Field Name TASK CONTROL BLOCK Hex. Dig. Field Description, Contents, Meaning 32 TCBFRS Floating point register save area .• o (0) 4 TCBRBP Address of the RB for executing program. 4 (4) 4 TCBPIE Address of the Program Interrupt Element (PIE). 8 (8) 4 TCBDEB Address of the queue of DEBs. 12 (C) 4 TCBTIO Address of the Task I/O Table (TIOT). 16 (10) 4 TCBCMP Task completion code. 20 (14) TCBTRN A byte used for flags as described: 20 (14) 1 (Reserved Bits) Suppress taking checkpoints for this step • Job step TCB-MFT, ••• x xxxx . 1 •. •• 1. MVT: This is a graphics foreground job or the graphic job processor. Both TESTRAN and decimal simulator programs being used on a Mod 91 machine. 1 .• '. . ... 21 (15) • 3 24 (18) 1 TESTRAN: TCBNROC MVT Job Step TCB: 00 nz (19) • 3 TCBMSS Address of control core table. Roll-out Eligibility. This job step may be rolled out. This job step may not be rolled out. (nz - A non-zero digit.) PCP, MFT: Address of the boundary box. MVT: Address of last subpool queue element (SPQE) 28 (lC) 1 TCBPKF xxxx 0000 29 (lD) • 5 TCBFLGS Storage storage Storage Must be protection key for this task. If there is no protection, all bits are zero. protection key Must be zeros. zeros. Flag byte fields. The use of this field in PCPandMFT differs from its use in MVT. PCP, MFT Use: 29 (lD) Byte 1 Abnormal termination in progress. Normal termination in progress • ABEND was initiated by the resident abnormal termination routine. Recursion through ABEND is permitted • 1 ••• • 1 •• •• 1. .•• • 1 1 ••• • 1 .• •• 1. ••• 1 242 OS System Control Blocks MFT: Graphics Abnormal Termination routine has been entered for this task~ CLOSE initiated by ABEND • Problem program storage has been overlaid to process ABEND. Prohibit queuing of asynchronous exits for this task • ( Offset Bytes and Alignment TASK CONTROL BLOCK Hex. Dig. Field Description, Contents, Meaning Field Name TCBFLGS (Continued) PCP, MFT Use (Continued): 30 (lE) Byte 2 1,. '. '. .xx. • '. x. •.• 1 1 ••. ,.1 •• •• .1 31 (IF) Byte 3 x'•• x ••• x ,.1 •• '. ,.1. 1,•• '. • 1 •. •• 1. 32 (20) Bytes 4-5 system task: ABEND prohibited for this task. (Reserved bits) Task has issued a system-must-complete and set all other tasks in the system non-dispatchable. Task has issued a step-must-complete and turned off all other tasks in the step. Dump processing has been initiated in ABEND. MFT: This task is a member of a time-sliced group,. (Reserved bits) MFT: Res erved. Exit Effector: system error routines already operating for this task. Floating pofnt registers exist. Job scheduler routines in process • XCTL routine is changing the storage protection key in the PSW from zero to the one used by the problem program. Reserved MVT Use: 29 (10) Byte 1 1 ..• • 1 •• •• 1,. •• ,.1 1 ••• • 1 •• •• 1. o •• 1 Abnormal termination in progress. Normal termination in progress • Enter Erase routine in ABEND when ABEND in control again. Enter Purge routine in ABEND when ABEND in control again. Graphics Abnormal Termination routine is in control of this task. (Bit 7 of byte 3 must also be on.) Top task in tree being abnormally terminated • Abnormal termination dump has been completed • Asynchronous exits cannot be scheduled. TCB 243 Offset Bytes and Alignment Field Name TASK CONTROL BLOCK Hex. Dig. Field Description. Contents. Meaning TCBFLGS (Continued) MVT Use (Continued): 30 (lE) Byte 2 1. '•• ,.1 •• '. ,.1. '. ,. ,.1 1 ••• • 1 •• •• 1. • •• 1 31 (IF) Byte 3 1. '. '. .1 •• • ,.1. • • ,.1 • •• x 1 •• x ,.1 •• • .1x '••• x x.xl 32 (20) Byte 4 1 ••• .1. '. • ,.1. ••• x xx •• • ,.1. • 33 (21) <4 •• • '•• 1 Byte 5 1 ••• • 1 •• '. ,.1,. • • ,.1 1 ••• .1 •• • ,.1. • •• x 244 Operands of ABEND macro instruction have been saved in TCBCMP field. Initiator TCB: Second job step interval has expired. Job Step TCB: Job step can cause rollout,. System must complete. Current task can be performed; other tasks in system cannot. Step must complete; other tasks in job step cannot be performed. Job step TCB: SYSABEND already open • ETXR exit requested by attaching task • Task is a member of a time-sliced group. OS System Control Blocks All PSWs for this task in supervisor state. Job step TCB: Job step has invoked rollouts that are still in effect. Prevent multiple ABEND. OPEN issued for SYSABEND. (See also bit 7.) ABDUMP in process for this task. (See also bit 7.) Job step TCB: No abnormal termination dumps can be provided within this job step. CLOSE has been issued during ABEND processing. (See also bit 7.) Valid reentry to ABEND indicated if bits 3. 4. or 6 of this byte or bit 4 of byte 29 is also on. (If any bit in this byte is 1, the task is non-dispatchable.) Set by ABDUMP. Machine check occurs. All tasks except current task placed in wait state. Supply of I/O request queue elements exhausted. (Reserved bits) M65 Multiprocessing: Task has been set non-dispatchable by one CPU to prevent any CPU from working on it. ABEND routine was entered by this task while DCB for SYSABEND was being opened for another task. (If any bit in this byte is 1. the task is non-dispatchable.) Terminated. To be terminated by ABEND • A routine of this task has issued an unconditional GETMAIN which must be satisfied by rollout of another job step. The job step has been rolled out. Another task is in system-must-complete status. Another task in this job step is in step-mustcomplete status. Initiator task: request for a region could not be satisfied. Reserved ( Offset 34 (22) Bytes and Alignment •• 1 Field Name TCBLMP TASK CONTROL BLOCK Hex. Dig. Field Description, Contents, Meaning PCP, MFT: Number of resources for which this task is enqueued .• MVT: Limit priority. 30 (23) ••• 1 TCBDSP Dispatching priority for this task. 36 (24) 4 TCBLLS PCP, MFT: Address of the most recently added RB on the list of programs loaded via the LOAD macro instruction. MVT: Address of load list element (LLE) for program loaded via the LOAD macro instruction,. 40 (28) 4 44 (2C) 4 44 (2C) 4 44 (2C) TCBJLB Address of a JOBLIB DCB. PCP, MFT: Reserved TCBJPQ MVT: Job step TCB: Byte 1 1,••• .xxx xxxx 45 (2D) Bytes 2-4 44 (2C) 4 48 (30) 64 112 (70) 1 Purge flag. (Reserved bits) Address of last entry in contents directory for job pack area (JPA) control queue. Other TCBs: Zero. TCBGRS General register save area. TCBIDF (One of these:) PCP, MFT: TCB identifier field. TCBQEL MVT: Number of resources for which this task is enqueued. 113 (71) • 3 TCBFSA Address of the first problem program save area. 116 (74) 4 TCBTCB Address of next TCB of lower priority on the ready queue. 120 (78) 4 TCBTME Address of the timer element. 124 (7C) 4 PCP: Reserved TCB 245 TASK CONTROL BLOCK Offset 124 Bytes and Alignment (7C> Field Name TCBPIB Hex. Dig. Field Description, Contents, Meaning A field used for two items of information. Partition type. 124 (7C) 1 00 •• 01 •• 10 •• 11. '. •• 1. • '. 0,. • ,•• x xxxx 125 (70) • System task partition. Reader partition. Writer partition. Processing program partition. Large partition • Small partition • (Reserved bits> Address of the partition information block (PIB). 3 MVT: 124 (7C) 4 TCBJSTCB Address of the first TCB for a job step. For tasks with a protection key of zero, this field contains the address of this TCB. PCP, MFT: Reserved (See Note A> 128 (80) 4 TCBNTC MVT: Address of the previous TCB on the originating task's subtask queue. The TCB for the last subtask has zeros in this field. PCP, MFT: Reserved (See Note A) 132 (84) 4 TCBOTC MVT: Address of the TCB for the originating task. PCP, MFT: Reserved (See Note A) 136 (88) 4 TCBLTC MVT: Address of the ·last TCB on the subtask queue for this task. The TCB for the last subtask has zero in this field. PCP, MFT: Reserved (See Note A) 140 (8C) 4 TCBIQE MVT: Address of an interruption queue element (IQE) for scheduling the ETXR routine on the originating task. PCP, MFT: Reserved (see Note A) 144 (90) 4 TCBECB MVT: Address of the ECB that will be posted by the supervisor' $ task termination routines when normal or abnormal termination occurs. PCP, MFT: Reserved (See Note A) 148 (94) 4 TCBSTAE Reserved (See Note A) PCP, MFT: Reserved (See Note A) ( 246 OS System Control Blocks Offset 152 (98) Bytes and Alignment 4 Field Name TCBPQE TASK CONTROL BLOCK Hex. Dig. Field Description, Contents, Meaning MFT: Address of the region dummy partition queue element minus 8 (DPQE-8). PCP, MFT: Reserved (See Note A) 156 (9C) 4 TCBAQE MVT: Address of an allocated queue element (AQE). PCP, MFT: Reserved (See Note A) 160 (AO) 1 TCBNSTAE • 3 164 168 (A4) (A8) 4 4 Flags internal to STAE routine. Address of the current STAE control block. PCP, MVT: TCBTCT Reserved. MFT: CPU time used by the step, in 26 micro-second time units. TCBUSER A field available to the user. Note A: Bytes 128-159 are overlayed by other system control blocks in PCP and MFT to conserve main storage space. TCB 247 ( Task Input/Output Table The task input/output table (TIOT) is constructed by job management routines. It resides in the higher portion of the dynamic area of main storage during step execution. The TIOT provides the I/O support routines (OPEN,CLOSE,EOV) with pointers to JFCBs and allocated devices. Figure 33 shows the format of a TIOT. Descriptions of the fields follow the illustration. TIOT 249 TASK INPUT/OUTPUT TABLE 1 TIOCNJOB Job Name 10(0) 1.(81 TIOCSTP Job Step Name, Procedure Step Name 1'6(101 For a Procedure Step: Job Step Name T 23 (17) I IT i::.:.£>'['--':::~!~l ..........................................................................----------------------------------------------. -------------------------------------------------" ___, +0 +1 TlOELNGH Length of DD Entry +2 +2 TlOESTTA Status Byte A _~4 TIOERLOC TIOEWTCT 1+3 TlEOLINK No. of Devices Requested Allocation: Link - Close: Flag - TlOEDDNM DD Name +12 TIOEJFCB Relative Address of JFCB, or of SlOT roo, +15 TlOESTTC Status Byte C Device Entry TlOESTTB Status Byte B +0 I +1 TIOEFSRT During Allocation: 2 Offsets During Problem Program: Address +3 rI-- I I -------------------------------------------- .. _--------_ .. _-_ .... -----------------------------, ... - ........... -- -- .. -- .. -- -- ........ -- ...... -~ Zero-End-of-TI OT Indicator Figure 33. Task Input/Output Table ( 250 OS System Control Blocks TASK INPUT/OUTPUT TABLE Offset Bytes and Alignment Field Name Field Description.. Contents. Meaning TIOCNJOB Job name. o (0) 8 (8) 8 (8) 8 For a job step that is not a procedure step: Job step name. For a job step that is a procedure step: Procedure step name. 16 (10) 8 For a job step that is not a procedure step: (Field not used.) For a job step that is a procedure step: Job step name of the job step that called the procedure. 8 TIOCSTEP DD Entries: There is a DD entry for each DD statement in the Job step or procedure step,. (References to GDG (all) data sets. the JOBLIB data set or PGM=*.ddname create still other DD entries,.) DD Entry: A DD entry includes a device entry. Before allocation. there may be several device entries in each DD entry. +0 1 TIOELNGH Length, in bytes. of this DD entry (including all device entries). +1 . 1 TIOESTTA Status Byte A. x... .x .. O. •• .0. ,. 0,. •• ..1 •• 1 .... ,.. 0 •• ,.1. '. • • 1. • ••• ••• 1 1 .... '•• 1. .... 1 +2 • • 1 +3 .. • . 1 Tape label processing to be performed: NL, BLP. SL, SUL. NSL. During allocation: Split cylinder primary. (This is the first DD entry for a split cylinder.) During step termination: No unallocation necessary. During allocation: Split cylinder secondary • (This is not the first DD entry for a split cylinder. ) During step termination: Rewind but no unloading. JOBLIB indicator • DADSM allocation necessary. Keep. catalog, uncatalog. Data set to be deleted • TIOERLOC (A 2 byte field consisting of:) TIOEWTCT During allocation: Number of devices requested for this data set. TIOELINK x ... .. 1 ... . During allocation: Link to the appropriate prime split. unit affinity. volume affinity or suballocate TIOT entry. After CLOSE: This is a SYSOUT data set that contains data. .. xxx xxxx (Reserved bits) x .... . 1 ... '. TIOT 251 TASK INPUT/OUTPUT TABLE Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DD Entry (Continued) +4 8 TIOEDDNM DD name. +12 3 TIOEJFCB Relative track address (TTR) of the JFCB. (During allocation, TTR of the SlOT if suballocate was requested. ) +15 .. TIOESTTC Status Byte C. Used during allocation only. zeros at end of allocation.. • .. 1 1,••• ,.1. '. '. ·.1. '••• 1 1 ... • 1,. ,. •• 1. ••• 1 Set to Secondary suballocate .• Deferred mount. Primary unit affinity. Secondary unit affinity. Primary volume affinity. Secondary volume affinity,• Primary suballocate • Data set to be passed • DEVICE ENTRIES During allocation: 1 device entry for each device required, or for each public device eligible. During problem program: 1 device entry for each allocated device. +0 1 TIOESTTB 1 •• '. ,.1 •• • ,.1. '•• ,.1 1 •.• .x,•• • 1 ... • 0 •• •• 1. • .. .. 1 +1 • 3 TIOEFSRT During allocation Status byte B During allocation and during problem program: Data set is on device. Data set will use device. Device violates separation • Volume serial present. Setup message required. Disposition: Retain unloaded volume if unload required • Delete unloaded volume if unload required • Unload required • Verification required • Bits 0 - 11: Offset, in the UCB look-up table, to an address for a device required or eligible for this data set.. For other than a 2321, the UCB look-up table has addresses of UCBs .. For a 2321 data cell drive, its addresses are those of the descriptions in the UCB of cells in bins .. Bits 12 - 23: Offset, in the step volume table (VOLT), to the volume serial number for the volume required or eligible for this data set. During problem program: Devices other than 2321: Address of the UCB. 2321 data cell drive: Address of the description in the UCB of the cell in the bin. (The description of the cell in hin 0 begins at UCB + 56.) END-OF-TIOT INDICATOR 4 252 OS System Control Blocks Binary Zeros. ( Unit Control Block There is a unit control block (UCB) for each device attached to the system. It describes the characteristics of the device to the I/O supervisor and is used by the job scheduler during allocation of the device. Figure 34 shows the format of the UCB. Descriptions of the fields follow the illustrations. The field descriptions of the UCB are followed by a diagram and detailed descriptions of the UCBTYP field of the UCB. The unit control block consists of two segments: a segment common to all devices (common segment) and a segment that varies with different devices (device-variable segment). The following illustrates the relationship of these segments. 0(0) Common Segment 24 (18) Device-Variable Segment: - UCS Graphic Devices Magnetic Tape Direct-Access Storage Data Cell Drive UCB 253 UNIT CONTROL BLOCK M65MP Prefix I~ UCBFL3 M65MP Flags 1- 3 Reserved -1 Common Segment 0(0) SRTEJBNR Internal Job No. 1 (1) SRTECHAN Allocation Channel Mask 2 (2) UCBID Identifier 3 (3) SRTESTAT Status Byte A 4 (4) UCBCHA Channel Address 5 (5) UCBUA Unit Address 6 (6) UCBFL1 Flag Byte 1 7 (7) UCBDTI Index to Device Table 8 (8) UCBETI Error Routine Key 9 (9) UCBSTI Statistics Table Index 11 (B) UCBATI Attention Table Index 12 (C) 10 (A) UCBLCI Channel Table Index 13 (D) UCBWGT Flags and Mask UCBNAME Unit Name 16 (10) UCBTYP Device Type 20 (14) UCBLTS Last Request Element ~_~yice - ___ Var_~~~le ~_~_9~_~~! ~_~_~ 22 (16) __________________________________________________________________________________________________________________________________________ _ 24 (18) 28 (lC) UCBSNS Sense Information UCBUCSID UCS Image Name UCBUCSOP UCS Image Format 29 (lD) Reserved 31 (IF) Graphic Device 24 (18) 26 (lA) 27 (lB) Additional Sense Information Use Count (GCB) Control Byte 28 (lC) Task Entry Address 32 (20) Restart Address 36 (24) 37 (25) Device Index Buffer Tabl e Address 39 (27) l ............ ________ ....... __ ....... _____ .... _ ........... __ .. ___ ... __ .. __ .............. _ .. __ ......... __ ... __ ............... ______ ........ __ .... ________________ ,. _________ ........... ________ .. _____ ....... ____ .. ___________________ .. ______________________________ .• ___________ ,) -Figure 34. Unit Control Block (Part 1 of 3) ( 254 OS System Control Blocks UNIT CONTROL BLOCK Magnetic Tape 24 (18) Additional Sense Information 28 (lC) SRTEVOLI Volume Serial No. 34 (22) 36 (24) SRTESTAB Status Byte B 38 (26) SRTEFSCT Sequence Count 35 (23) SRTEDMCT Vol M Sw I DCB Count SRTEFSEQ Sequence No. 40 (28) Data Set Serial Number 46 (2E) Reserved _,,,48 (30) T Irec t UCBROR Read-Opposite Recovery CCW -~ 55 (37)T . Access St orage DeVlce (E xcep t Da tell a e Drive 24 (18) Additional Sense Information 28 (lC) SRTEVOLI Volume Serial No. 34(22) 36 (24) 40 (28) 35 (23) SRTEDMCT No. of DCBs Open SRTEFSCT Relative Address of VTOC UCBSQC RESERVE Count 41 (29) UCBDVRES Device Reservation Indicator -- -.A8 (30) 56 (38) SRTESTAB Status Byte B 42 (2A) Reserved -... UCBSKA Direct-Access Address of Lost Seek SRTEUSER No. of Users 57 (39) SRTEECBA Direct Access ECB Address ~60 (3C) -... Error Recovery Work Area I lOO(MI ) 1 Overflow Work Area (Present When Overflow Specified) 139 (8811 : Continued : ,--------------------------------------------------------------------------------------------------------_ .... --------------------------.,-------------- .. ---------------------------------_ ....... __ .... _--------- ... eFigure 34. Unit Control Block (Part 2 of 3) UCB 255 UNIT CONTROL BLOCK ! r----2j2;---Oo-ta---ce-ff--orlv-e----------------------------------------------------------------------------------------------------------------------------------------------------------1 ':.;, 124 _ Additional Sense Data (18) :T lL~ _ J 1 28 (lC) : Error Routine Work Area A 1 ~8 I Re~'Ved (30) ! UCBSKA Seek Address Last Used T Description of Cell in Bin 0 56 (38) DCELBBNR Bin Number 59 (3B) 58 (3A) DCELSTAB Status Byte B DCELSTAT Cell/Bin Status I-I-- 60 (3C) I-- DCELVOLI Volume Serial Number - 66 (42) DCELJ BNR Internal Job Numbers r- 67 (43) DCELDMCT No. of DCBs Open ~ 68 (44) DCELVTOC Relative Address of VTOC - 71 (47) DCELUSER Allocated Data Sets I-- I Cell in Bin 1 I 87 (57) Cell in Bin 2 I 103 (67) Cell in Bin 3 I 119 (77) Cell in Bin 4 I 135 (87) 151 (97) Cell in Bin 5 I 167 (A7) Cell in Bin 6 I Cell in Bin 7 I Cell in Bin 8 I Cell in Bin 9 ,1 215 (D7) -__ Error Routine Work Area B 124B (FB) Error Routine Work Area for Track Overflow , 199 (C7) 1 ",,-216 (D8) T .... - - . . _ _ . . . . . . . . . . . . . . - ' ' ' ' ' _ 183 (B7) . . _ _ _ _ . . . . . . _ _ _ ... _ Figure 34. .......... __ .... _ .... ____ .. __ .. _ . . 00 . . . . . . . . . . . . . . . . . . _ . . . . _ _ _ _ ".. _ _ . . _ _ _ _ . . . . . . . _ _ . . _ _ _ ...... _ _ _ _ . . _ _ . . . . . . . . . . . . . . . _ . . _ _ _ ........... _ ......... _ .. _ ....... - . . - - ..... _ _ _ _ . . . . _ _ _ _ _ _ ... _ _ _ _ _ _ . . . . . . _ _ . . . . _ I , ..... _ _ _ . . _ _ _ _ _ . . . . . . . . . . . _ _ _ _ . . . . . _ _ _ . . . . _ _ .. _ _ _ _ _ . . . . . . . . . . . . . . . . . . . . . . . _ - _ . . . . unit Control Block (Part 3 of 3) ( 256 OS System Control Blocks UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning PREFIX SEGMENT Present only if M65MP was specified in the system generation (SYSGEN) process. -4 (-4) UCBFL3 Byte 1 xx ••• x •• · '.• 1 • .1,. 0 ..... 1 •• '. • ,.1-. '••• 1 -3 (-3) Bytes 2-4 Model 65 Multiprocessing flags,. (Reserved bits) CPU A is to use an HIO instruction CPU B is to use as HIO instruction CPU A last used an SIO instruction CPU B last used an SIO instruction CPU B has no path to this device • CPU A has no path to this device. for for for for this this this this device. device,. device. device. Reserved SEGMENT COMMON TO ALL DEVICES o (0) 1 SRTEJBNR Internal job identification. 1 (1) • 1 SRTECHAN Allocation channel mask. 2 (2) '.. 1 UCBID UCB identification - Hex FF. 3 (3) SRTESTAT Status byte A. Device status flag: Device is offline. Device is online. Device is to be changed from online to offline status. Reserved, that is, the mount status of the volume on this device is reserved. (See note A.) UNLOAD operator command has been addressed to this device; the device is. not yet unloaded. Device is allocated. Permanently resident, that is, the mount status of the volume on this device, is permanently resident. (See note A.) One of these: This is the systems residence device. This is the primary console. One of these: Standard labels have been verified for this tape volume. This is the alternate console. • 1 x. '. '. 0,••• 1,•• '. .1 •• • ,.1,. • '•• 1 1 ••• .1 •. .,.'.'• • ,.1. '.'.-.'. . . . 1 Note A: If the mount status is neither reserved nor permanently resident, then i t is removable. 4 (4) UCBCHA 1 1 ••• • 1 .•. .-.xx x •• '. ,.xxx 5 (5) • 1 UCBUA Channel address. Halt I/O. Status modifier,• (Reserved bits) Channel address - binary number. Unit address. » UCB 257 UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning SEGMENT COMMON TO ALL DEVICES (Continued) 6 (6) •• 1 UCBFLl 1,...... . 1 •. '.I.X. '.... 0,. '. ,.. 1,. ,•.• ,.1 1 .. '•• .. xx .. .01. .11. .01 .. '••. 1 7 (7) ..oo 8 (8) 9 Flag byte 1. Busy - Device status. Not-ready - Device status .. Post flag. No channel program is being executed using this device,. A channel program using this device has not yet been posted as having completed. After a channel end status a separate device end status occurred with an error indication. (IOBIntercept flag.) Busy - Control unit status. Direct access storage devices: Stand-alone channel program of I/O supervisor is being or was executed. (Arm seeking.) User's channel program is being executed. (Data transfer. ) Telecommunications devices: Inhibit HIO instruction because the line is in receive status. I/O error routine is in control of this device. No other I/O operations are permitted on this device. UCBDTI Index to the Device Table. 1 UCBETI A binary number used by the exit effector routine to complete the 8 byte name of an IBM-supplied error routine for this device. (9) • 1 UCBSTI Increment which, when multiplied by 10, becomes an index to the statistics Table (STATAB). 10 (A) 'OO. UCBLCI Increment which, when multiplied by 8, becomes an index to the Logical Channel Table (LCHTAB). 11 (B) • UCBATI Index to the Attention Table (ANTAB). 12 (C) 1 UCBWGT Flags and channel mask. 'OO 1 1 • 1 1 .... .. ,.1 .... '. ,.. 1,. '. '•.• 1 xxxx 1,. '.... • 1 .•• '•.• 1. '. '... 1 SYSIN. SYSOUT. Assumed that this device will be allocated for a public volume request. Rewind command has been addressed to this magnetic device by I/O support. I/O Supervisor path mask. (Used where there are two or more paths to a device): Primary path to the device is inoperative. Optional path 1 to the device is inoperative • Optional path 2 to the device is inoperative. Optional path 3 to the device is inoperative. ( 258 OS System Control Blocks UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning SEGMENT COMMON TO ALL DEVICES (Continued) 13 (D) 16 (10) • 3 UCBNAME Unit name (EBCDIC). 4 UCBTYP Device type. THIS FIELD IS DESCRIBED SEPARATELY AND IN DETAIL AT THE END OF THE DESCRIPTION OF THE OTHER UCB FIELDS. 20 (14) 2 UCBLTS Last Request Element. 22 (16) •• 2 UCBSNS Sense information for all devices. DEVICE-VARIABLE SEGMENT UCS Seqment This segment is present if the system generation process specifies the universal character set (UCS) feature. Else, no device-variable segment is present for unit record devices. 24 (18) 4 UCBUCSID Name of the UCS image in the buffer. 28 (lC) 1 UCBUCSOP Format of the UCS image in the buffer. 1 .• '. . 1 •• •• xx xxxx 29 (10) • 3 UCS image is the default image. UCS image is in the FOLD mode • (Reserved bits) Reserved GRAPHIC DEVICES 24 (18) 2 Additional Sense information. Use Count 26 (lA) •• 1 Number of DCBs that are currently open for this device. GCB 27 (lB) ••• 1 Graphic control byte used for attention handling. Task Entry Address 28 (lC) 4 Address of task entry (TE) block. Restart Address 32 (20) 4 Last start address. Device Index 36 (24) 1 Device or devices on a control unit to which buffer sections are assigned. Buffer Table Address 37 (25) • 3 Address of buffer table. UCB 259 UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning MAGNETIC TAPE DEVICES 24 (18) 4 Additional Sense information. 28 (lC) 6 SRTEVOLI Volume serial number. 34 (22) •• 1 SRTESTAB Status byte B - Volume status. x •• '. O•• '. 1 ••• .x ••• xxx • ,.1. . '... 1 1 ..• 35 (23) ••. 1 SRTEDMCT 1 ••• 0 ••••••• 0 ••• O•• '. • xxx xxxx Volume sharability: Sharable. Not sharable. (Reserved bits) Additional volume label processing,• Private - Volume use status • Public - Volume use status. Volume mount switch. This switch shows whether a volume has been mounted and whether the volume label found on the volume has been verified to be the type specified by the DD statement parameter.. (DD Stat. Parm.) DD Stat. Parma ---- Any Scheduler: No volume has been mounted. A volume has been mounted but no volume label processing has been performed. (Normal scheduler processing, effective with release 11.) SL Open routine: Volume label is not standard format or serial number is not correct. (A mount message has been issued.) Standard volume label and correct serial number has been verified. NSL Open routine: Volume label is not standard format. (Control passes to the processing program's nonstandard label processing routine.) Volume label is standard format. (Control remains with the Open routine. A mount message has been issued.) Processing program: Non-standard volume label has been verified. NL Open routine: Standard volume label has been found. (A mount message has been issued.) No standard volume label has been found. BLP Open routine: Volume label has not been processed. Number of DCBs open for this volume • 36 (24) 2 SRTEFSCT Data set sequence count. 38 (26) •• 2 SRTEFSEQ Data set sequence number. 40 (28) 6 Data set serial number. 46 (2E) •• 2 Reserved for future use. 48 (30) 8 260 UCBROR OS System Control Blocks CCW for opposite-direction recovery. ( UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description, Contents, Meaning DIRECT ACCESS STORAGE DEVICE (EXCEPT DATA CELL DRIVE) 24 (18) 4 28 (lC) 6 SRTEVOLI Volume serial number. 34 (22) •• 1 SRTESTAB status byte B - Volume status. Additional Sense information. x ••• 0 ••• 1 •.• • xx .• . • .• 1 1 ••• • 1 •• •• 1. ... 1 Volume sharability: Sharable. Not sharable. (Reserved bits) Private - Volume use status • Public - Volume use status. Storage - Volume use status • Joblib data set is on this volume • Control volume - A catalog data set is on this volume. 35 (23) ••. 1 SRTEDMCT Number of DCBs open for this volume. 36 (24) 4 SRTEFSCT Relative address of VTOC for this volume, in form TTRO. 40 (28) 1 UCBSQC Number of RESERVE macro instructions issued. 41 (29) • 1 UCBDVRES Device reservation indicator. In a system that includes the shared DASD option, this indicator is set equal to the contents of the UCBSQC field after a successful completion of an SIO instruction for a direct access storage device (DASD). 42 (2A) •• 6 48 (30) 8 UCBSKA Disk address (MBBCCHHR) for last seek. 56 (38) 1 SRTEUSER Number of current users. 57 (39) • 3 SRTEECBA Direct access ECB address. 60 (3C) 40 Error recovery storage and work area. 100 (64) 40 Track overflow work area. If track overflow is installed these additional bytes are always a part of a UCB. Reserved. 2321 DATA CELL DRIVE 24 (18) 4 Additional Sense information. Error Routine Work Area 28 (19) 12 A 40 (28) 8 Reserved 48 (30) 8 UCBSKA work area for the error routine. Address for last Seek, in the form MBBCCHHR. (2321 DATA CELL DRIVE SEGMENT CONTIIWES) ) UCB 261 UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field Description l Contents, Meaning 2321 DATA CELL DRIVE (Continued) Description of cell in bin 0 56 (38) 2 DCELBBNR Bin number .. 58 (3A) .... 1 DCELSTAB Status byte B - volume status. X'• • • 0,.. '. '. 1 .. '•• .xx .. '.•• 1 1. '... ,.1. ,. .. 1. I• • • 59 (3B) ..... 1 1 DCELSTAT 1,... ,. o.... '. .. x. '... -.xx '. ,.1,. ••• 1 1 .•• .• 1 .... Volume sharability: Sharable. Not sharable .. (Reserved bits) Private - Volume use status .. Public - Volume user status .. Storage - Volume use status. Joblib data set is on this volume .. Control volume - A catalog data set is on this volume. Cell/Bin status. Bin is online and a normal cell is mounted in it,.. Bin is offline or a ballast cell is mounted in it. (Reserved bits) Reserved.. - Mount status of the cell in this bin,. (See note A.) UNLOAD operator command has been addressed to this bin; the bin has not yet been unloaded. Bin is allocated. Permanently resident,. - The mount status of this cell. (See note A.) Note A: If the mount status is neither reserved nor permanently resident, then i t is removable. 60 (3C) 66 (42) 67 (43) 68 (44) 71 (47) DC EVOL I Volume serial number. 1 DCELJBNR Internal job number. • 1 DCELDMCT Number of data sets opened for this cell. 3 DCELVTOC Address of VTOC, in form TTR .. '• • • 1 DCELUSER Number of data sets allocated to this cell. • 6 End of Description of cell in bin o. ( 262 OS System Control Blocks UNIT CONTROL BLOCK Offset Bytes and Alignment Field Name Field DescriptioD 1 Contents, Meaning 2321 DATA CELL DRIVE (Continued) 72 (48) 16 Description of Cell in Bin 1 (Same format as description of cell in bin 0). 88 (58) 16 Description of Cell in Bin 2 (Same format as description of cell in bin 0). 104 (68) 16 Description of Cell in Bin 3 (Same format as description of cell in bin 0). 120 (78) 16 Description of Cell in Bin 4 (Same format as description of cell in bin 0). 136 (88) 16 Description of Cell in Bin 5 (Same format as description of cell in bin 0). 152 (98) 16 Description of Cell in Bin 6 (Same format as description of cell in bin 0). 168 (A8) 16 Description of cell in Bin 7 (Same format as description of cell in bin 0). 184 (B8) 16 Description of Cell in Bin 8 (Same format as description of cell in bin 0). 200 (C8) 16 Description of Cell in Bin 9 (Same format as description of cell in bin 0). Work Areas Error Routine Work Area 216 (08) 32 A work area used by the error routine. Error Routine Work Area for Track Overflow 288 (120) 40 A work area for the error routine, present and used only if track overflow has been specified. UCB 263 ( The UCBTYP Field in the UCB The UCBTYP field completely describes the device type. It is the exact analog of the full device name, except that it includes terminal adapters and similar units when they are part of the necessary description. Figure 35 shows the type of entries in the field. Following the illustration, the field is described separately by type of entry and by type of device. UCBTYP I lOS Flags Model Code I UCB + 16 (10) Figure 35. Offset Byte 3 Byte 2 Byte 1 Optional Features I Device Class 18 (12) 17 (11) Byte 4 I Unit Type 19 (13) The UCBTYP Field Bytes and Alignment Bit and state Hex. Pig. Field Description., Contents, Meaning ENTRY Devices Other Than Graphic Devices 16 (10) 1 xxxx I/O Supervisor flags. x .•• '. '.... 1 (Reserved bit) Overrunable device • Burst mode. Byte mode • Data chaining. xxxx Graphic Devices Device class. Byte 1 • 1,•• '•.• 1 .• • '. O. 13- 0001 0011 Model code,. See following description of UCBTYP field by device class. xxxx 17 18 (11) (12) 1053, 2260 2250 • 1 Byte 2 Optional features. See following description of UCBTYP field by device class. •• 1 Device class. Byte 3 08 10 20 40 80 19 (13) ••• 1 Byte 4 Unit Record. Graphics. Direct Access Storage,. Communication Equipment. Magnetic Tape. Unit type. See following description of UCBTYP field by device class. UCB 265 DESCRIPTION OF THE UCBTYP FIELD BY DEVICE CLASS: UNIT RECORD DEVICE CLASS UCBTYP Byte 2 Byte 1 lOS Flags I Model Code UCB + 16 (10) Offset 16 (10) I 1 Byte 1 Bit and State xxxx I/O Supervisor flags,. x .••• .• 1,•.• .• • 1,. • ,.0. (Reserved bit) Overrunable device,• Burst mode • Byte mode • Data chaining. Model Code. With 1442, 2520 Read Punch. Punch only. 0000 0001 -1 . Universal character set (UCS). (Reserved bits) Card image (binary mode) '. I. ,•• (12) .. Device Class. 2 Byte 3 08 19 (13) '. '. '. Unit Type 19 (13) Optional Features. 1 Byte 2 1 •• '. • xxx xxx • 1 18 I Hex. Dig. Field DescriEtion, Contents, Meaning xxxx (11) Device Class 18 (12) '•.• ,.1 17 I Optional Features 17 (11) Bytes and Alignment Byte 4 Byte 3 3 Unit record. Unit Type. Byte 4 01 02 03 04 05 08 OA 10 20 21 2540 2540 1442 2501 2520 1403 1404 1443 2671 1052 2150 Card Reader. Card Punch. Card Read Punch. Card Reader .• Card Read Punch,. Printer (models Nl., 2, 3, 7) and Printer (continuous form support only). Printer (model Nl only). Paper Tape Reader. Printer-Keyboard. Console. ( 266 OS System Control Blocks MAGNETIC TAPE DEVICE CLASS UCBTYP Byte 2 Byte 1 lOS Flags UCB I Model Code + 16 (10) offset (10) 16 Byte 1 I Optiona I Features 17 (11) Bytes and Alignment Bit and State 18 19 (11) xxxx x.xx .1 •• I/O Supervisor flags. (Reserved bit) Overrunable device • Burst mode • Byte mode • Data chaining • Model Code. (Reserved bits) Phase-encode code (Models 4., ••• x xxxx Optional Features. 7-track compatibility ( 2400) Data conversion (2400) Dual-density (2400) (Reserved bits) o••.• (12) (13) . 1 Byte 2 '. . Device Class Byte 4 I 1. '. ,. .1 .. .•.• 1,. 5, 6, 7) Byte 3 80 Device Class. Magnetic Tape. . '. . 1 01 Unit Type • 2400 Series Magnetic Tape Device. 1 Byte 4 Unit Type 19 (13) Hex. Dig. Field DescriEtion, Contents, Meaning • 1 •• .• • 1 .• .•.• 0 .• •• ,.1 11 I 18 (12) xxxx 1 Byte 3 ) UCB 267 DIRECT ACCESS STORAGE DEVICE CLASS UCBTYP Byte 2 Byte 1 lOS Flags I Model Code UCB + 16 (10) Offset 16 (10) I Optiona I Features 17 (11) Bytes and Aligrunent Byte 1 1 Bit and state 19 (12) Optional Features. Scan feature. Track overflow. This device can be shared between two or more CPUs,• (Reserved bits) • 1 1 ••• ,.1. I. '.. 1 Byte 3 20 Device class. Direct access storage device. 01 02 03 04 05 08 Unit 2311 2301 2303 2302 2321 2314 (13).. 1 Byte 4 Unit Type 19 (13) I/O Supervisor flags. (Reserved bit) Overrunable device • Burst mode. Byte mode • Data chaining • Model Code. xxxx .. 1. •·•.• x xxxx 18 I Dig. Field Description, Contents, Meaning 0000 Byte 2 Device Class Byte 4 Hex. . 1. '. '. ,.1 .• • • 0,. • '. ,.1 (11) I 18 (12) x ••• 17 Byte 3 type. Disk Storage Drive. Parallel Drum. Serial Drum,. Disk Storage. Data Cell Drive. Disk Storage Facility_ c ( 268 OS System Control Blocks GRAPHIC DEVICE CLASS - MODEL 2250 DISPLAY UNIT UCBTYP Byte 1 lOS Flags I Byte 2 Model Code UCB + 16 (10) Offset 16 (10) I Optional Features 17 (11) Bytes and Alignment 1 Byte 1 Device Class Byte 4 I Unit !ype 19 (13) Hex .• Dig. Field DescriEtion* Contents, Meaning J13-K -1 (11) I 18 (12) -2 -3 11 Byte 3 • 1 Byte 2 01234561- 89- AB- CDEF- Device Class 1056,2260 2250 Model Code Model 1. Model 2. Model 3. Optional Features Model 0Etional Features 1,2,3 No optional features. 1.2,3 programmed Function Keyboard only. 1,2 Light Pen only. 1,2 programmed Function Keyboard, and Light Pen. 1.2,3 Alphameric Keyboard only. 1,2,3 Programmed Function Keyboard and Alphameric Keyboard. 1, 2 Alphameric Keyboard and Light Pen .• 1,2 Alphameric Keyboard, Light Pen and programmed Function Keyboard. 1,2 Absolute Vector Graphics only. 1,2 Absolute vector Graphics and Programmed Function Keyboard. 1,2 Absolute Vector Graphics and Light Pen. 1,2 Absolute vector Graphics, Programmed Function Keyboard and Light Pen. 1,2 Absolute Vector Graphics and Alphameric Keyboard. 1, 2 Absolute vector Graphics., Programmed Function Keyboard and Alphameric Keyboard. 1,2 Absolute vector Graphic, Alphameric Keyboard, and Light Pen. 1,2 Absolute vector Graphics, Alphameric Keyboard, Light Pen and Programmed FUnction Keyboard. UCB 269 GRAPHIC DEVICE CLASS - MODEL 2250 DISPLAY UNIT Offset Bytes and Alignment Hex. Dig. Field Description, Contents, Meaning Model 17 18 (11) (12) (cont) Byte 2 (13) -1-- -1 -2 -3 -4 -5 -6 1 1 1 1 1 1 -7 1 -8 -9 1 1 -A 1 -B 1 •• 1 Byte 3 19 -0 10 ••• 1 Byte 4 02 Optional Features No optional features. 4K Buffer only .• 8K Buffer only. Character Generator only,. 4K Buffer and Character Generator. 8K Buffer and Character Generator. Graphic Design Feature only. Graphic Design Feature and 4K Buffer .• Graphic Design Feature and 8K Buffer. Graphic Design Feature and Character Generator. Graphic Design Feature. 4K Buffer, and Character Generator. Graphic Design Feature, 8K Buffer, and Character Generator. Device Class Graphics Unit Type 2250 Graphic Display Unit. c 270 OS System Control Blocks GRAPHICS DEVICE CLASS 2260 Display Station UCBTYP lOS Flags I Model Code UCB + 16 (10) Offset 16 17 (10) (11) I 17 (11) Bytes and Alignment 1 Byte 1 . J13- Device Class. 1053, 2260 2250 -K -1 -2 Model Code Modell. Model 2. Optional Features 23- 456789ABCDEF- -B -C -D -E 18 (12) '.. 1 Byte 3 Byte 4 I Unit Type 19 (13) Hex. Dig. Field Description, Contents, Meaning 1 Byte 2 (Cont) Device Class 18 (12) 1- (11) I Optional Features 0- 17 Byte 3 Byte 2 Byte 1 10 Optional Features No optional features. Line Addressing only. Numeric Keyboard only. Line Addressing and Numeric Keyboard. Alphameric Keyboard only. Line Addressing and Alphameric Keyboard. Non-destructive cursor only. Line Addressing and Non-destructive cursor. Numeric Keyboard, and Non-destructive cursor,. Optional Features Line Addressing, Numeric Keyboard and Nondestructive cursor. Alphameric Keyboard and Non-destructive Cursor. Line Addressing, Alphameric Keyboard and Nondestructive cursor. Data Entry Keyboard only,. Data Entry Keyboard and Line Addressing. Data Entry Keyboard and Non-destructive Cursor. Data Entry Keyboard, Line Addressing, and Nondestructive Cursor. 2848 Display Control, Model 1 with 240 character display capability. 2848 Display Control, Model 2 with 480 character display capability. 2848 Display Control, Model 3 with 960 character display capability. 2848 Display Control, Model 21 with 240 character display capability. 2848 Display Control, Model 22 with 480 character display capability. Device Class Graphics Unit Type 19 (13) ••• 1 Byte 4 03 2260 Graphic Display Unit. UCB 271 GRAPHICS DEVICE CLASS Other Than 2250 or 2260 UCBTYP Byte 1 lOS Flags I Byte 2 Model Code UCB + 16 (10) Offset Bytes and Alignment (10) 1 Byte 1 17 (11) • 1 Byte 2 19 (12) (13) Optional Features 17 (11) 16 18 I Byte 3 •• 1 Byte 3 ••• 1 Byte 4 I Device Class 18 (12) Byte 4 I Unit Type 19 (13) Hex. Dig. Field Description, Contents, Meaning J13-K -0 -0 -4 Device Class. 1053, 2260 2250 Model Code 2280 Film Recorder. 2282 Film Recorder Scanner. 1053 Printer, Model 4. Optional Features 00 00 00 Device 1053 2280 2282 10 Device Class Graphics 04 05 06 Unit 1053 2280 2282 No optional features. No optional features,. No optional features. Type Printer. Film Recorder. Film Recorder/Scanner. ( 272 OS system Control Blocks COMMUNICATION EQUIPMENT DEVICE CLASS UCBTYP Byte 2 Byte 1 lOS Flags I Model Code UCB + 16 (10) Offset 16 (10) I Optional Features 17 (11) Bytes and Alignment 1 Byte 1 Bit and State (11) I Device Class 18 (12) Byte 4 I Unit Type 19 (13) Hex. Dig. Field Description, Contents, Meaning xxxx I/O Supervisor flags x... .1.. •• 1. •• 0. ••• 1 (Reserved bit) Overrunable device • Burst mode • Byte mode • Data chaining. Model Code The value in this field and the value in the adapter type field (byte 4, bits 0-3) together identify the model,. Adapter ~ Model 11050 21030 31050 483B3 5TWX 82260 9S/360 11060 4115A 91130 92780 12740 1WTTA xxxx 17 Byte 3 •••• 0001 -1 ..... 0010 -2 0011 0100 0110 -3 -4 -6 . optional features. 1 Byte 2 1,••• • 1 •• •• 1. •• • 1 1 .•. • 1 •• .... '. •• xx Automatic calling. Automatic polling • Checking • Automatic answering • station control. Transmit control • Binary Value - 0 - SADZER SAD ONE 1 SAD TWO 2 SAD THREE 3 UCB 273 Offset 18 19 (12) (13) Bytes and A1ignment COMMUNICATION EQUIPMENT DEVICE CLASS Bit and Hex. State Dig. Field Description, Contents, Meaning .. '. . .4 1 Byte 1 Byte 3 40 123456789-1 -2 -3 Device Class. communication equipment. Adapter Type. IBM Terminal Adapter, Type I. IBM Terminal Adapter, Type II. IBM Telegraph Adapter. Telegraph Adapter, Type I. Telegraph Adapter, Type II. World Trade Telegraph Adapter,. Synchronous Adapter, Type I. IBM Terminal Adapter, Type III. Synchronous Adapter, Type II. Control unit 2702 2101 2703 c 274 OS System Control Blocks V olume Label A volume label is 80 characters long and identifies the volume and its owner. Figure 36 shows the volume label format. Description of the fields follow the ill ustration,. Magnetic tape volumes, the volume label is the first record on the tape. On ninetrack tape it is written in EBCDIC, on seven-track tape in BCD. On direct access volumes, i t is record number three, following the two IPL records if they are present" and is recorded in EBCDIC. Volume Label 275 VOLUME LABEL a (0) 3 (3) VOllABI label ID VOlNO label No. 4 (4) VOlSERNO Volume No. 10 (A) 11 (B) Reserv€d -" Ta p e: Reserved DASD: VOlVTOC - Address of the VTOC DSCB -c- 21 (15) ........ ..,,... Reserve d "'r- 41 (29) VOlOWNER Owner Name and Code 51 (33) ........ ........ Reserved T 79 (4F) Figure 36. Offset Volume Label Bytes and Alignment 0 (0) 3 3 (3) ·· 4 (4) 6 10 (A) ·· 11 (B) 11 (B) 16 (10) 21 (15) 20 41 (29) · 10 51 (33) · · · 29 276 J • 1 Field Name Field Description, Contents, Meaning VOLLABI Label identifier - VOL. VOLNO Volume label sequence number. VOLS ER NO Volume serial number. 1 Reserved - must be recorded as EBCDIC zero. VOLVTOC Magnetic Tape: Reserved - must be recorded as blanks. ···5 Direct Access Storage: The CCHHR address of the VTOC DSCB on this volume. 5 Reserved - must be recorded as blanks. Reserved - must be recorded as blanks. VOLOWNER OS system Control Blocks Owner name and address code for the owning installation. Reserved - must be recorded as blanks. ( Volume Table of Contents The volume table of contents (VTOC) is a data set consisting of data set control blocks (DSCB) '. The format of the VTOC" and its relation to user labels, is shown in Figure 37. A description follows the illustration. (The DSCBs are describes separately, under that heading, in this publication .• ) VTOC 277 I I Standard Volume Label VTOC Data Set Description of Device and Volume '--~ Description of Up to 26 Shared Cyl inders -- Description of Up to 26 Available Extents Format 4 DSCB -- - Format 6 DSCB I-- -Format 5 DSCB I 5 I 5 - r-- I -- rr- 6 I 6 Avai lable VTOC Space I-I-- -Format 0 DSCB I 0 I 0 Physical Sequential, Partitioned, Direct Organization - ...- Description of Data Set I Descriptions of 4th-16th Extents -- --- Format 1 DSCB Format 3* DSCB , _I 1 I 3* "'-I 1 -- ...- 3* Index Sequential Organization Data Sets - Description of Data Set Description of Indexing Elements I-- -- I User Label* , f-----I !1l User Label Extent* - 3* I Legend: , Volume Table of Contents OS system Control Blocks 3* "I ~ NOTES: S - User labels may only be used with physical sequential or direct organization data sets. * - Not a Iways present. 218 Format 3* DSCB , _I 2 .J • Figure 31. ~ 2 1 ...- --- Format 2 DSCB 1 S r- Descriptions of 4th-16th Extents I-- -- Format 1 DSCB I ...- EJ} Data Set Control Block 44 Byte Key Area 96 Byte Data Area Label - I} 80 Byte Data Area " - -_ _oJ c VOLUME TABLE OF CONTENTS The volume table of contents (VTOC) is a data set consisting of control blocks that describe the contents of a direct access storage device volume. (The data set has a single extent; its address is found in the standard volume label. See figure 36.) On secondary storage, the control blocks that make up this data set consist of a 44 byte key segment and a 96 byte data segment; in main storage, each forms a 140 byte block. Each 140 byte block makes up a data set control block (DSCB). To accomodate various categories of information about the volume and the data sets on it, the 140 byte blocks are formatted in different ways. DSCB formats 1, 2, 3, and 4 are designed for data set information; DSCB formats 5 and 6 describe the available or shared space. Space in the VTOC not occupied by one of these DSCBs is filled with format 0 DSCBs, which contain binary zeros. (For a detailed description of each format, refer to the DSCB section of this publication.) At the beginning of the VTOC is a single format 4 DSCB. It is followed by at least one format 5 DSCB. If there are any more format 5 DSCBs, they are chained from the first format 5 OSCB. If there are any format 6 DSCBs, they are chained from the format 4 DSCB. For every data set on the volume there is a format 1 OSCB, and also a format 2 OSCB if the data set has index sequential organization. Format 1 DSCBs are found by using a Search (Equal) command with an argument of the DSNAME operand; they are not chained to one another nor to the format 4 OSCB. If the data set has more than three extents, a format 3 DSCB is chained from the format 1 DSCB, or the format 2 OSCB in the case of index sequential organization,. Any space remaining in the VTOC extent carries format 0 OSCBs. User labels, if used, occupy the first extent described by a format 1 OSCB. This extent, a separate one for each data set~ is one track long; the labels form 80 byte data segments. VTOC 279 ( Index: Access method blocks and segments data control block ••••••••• 35,48,59,74 data event control block •••••••••••••• 101,103,107,111,113 data extent block ••••••••••••••••••• 91 input/output block ••••••••••••• 171,174 Appendage table block segment data extent block ••••••••.•••.•••••• 88 Common block segments data control block •••••• 31,44,56,72,79 data extent block •.••••••••.•• 89,96,97 Communication vector table ••••••••••••• 11 CVT (see communication vector table) CVT user field ••••••.•••••••••••••••••• 19 Basic block segments (see common block segments) BBCCHH (see MBBCCHHR) BDAM (see access method block segments) Binary Synchronous communication DC B- BT AM ••••••• _ • • ... • • • • • . • • • • • • • • •• 74 DECB-BTAM •••••••••• 117 BISAM (see access method block segments) Block segments (see the following:) access method block segments appendage table block segment basic block segment buffer request block segment common block segments device-dependent block segments DASD message queue block segments foundation extension segment foundation prefix segment foundation segment line control block segment line error block segment line group block segment MFT block segments, field uses MVT block segments, field uses polling list origin block segment processing message queue block segment queue control block segment receive scheduler sub-TCB block segment scheduling-dependent block segment subroutine identification block segment BPAM (see access method block segments) BSAM (see access method block segments) BSC (see binary synchronous communication) BTAM (see access method block segments) Buffer request block segment data extent block-QTAM •••••••••••••• 97 DADSM Interlock - UCB Deleted Data cell drive segment, field, flag data control block . . . . . . . . . . . . . . . 28,44 unit control block ••••••.•.•.•••••• 265 UCBTYP field ••••••••••••••••••••••• 265 DASD (direct access storage device) message queue block segment (extension, interface) data control block •••••••••••••••••• 65 data extent block (destination queue) 91 Data control block ••••••••••••••••••••• 21 BDAM •••••••••••••••••••••••••••••••• 53 BISAM •••••••• _ ••••••• '••.•••••••••• Q. 39 BPAM ................................. 23 BS]I,M .................................. 23 BTAM ••••••••••• '. • • • • • • • • • • • • • • • • • • •• 69 EXCP access method ••••••.••••••••••• 23 GAM •••• '. • • • • • • • • • • • • • • • • • • • • • • • • • • •• 77 QI SAM ................ ,........... '••• '. •• 39 QSAM. ................................... 23 QTAM ............................ '. • • ... 61 Data event control block ................ 99 BDAM ................................ 107 BSAM ......................... '. • • • .. • •• 101 BTAM ••••••••••••••••••••••••••••••• 113 I SAM ............ _ . • • • • • • • • • • • • • . • • • • •• 103 QT AM .................. 111 Data extent block •••••••••••••••••••••• 81 appendage table ••••••••••••••••••••• 88 ordinary •..•...•.....•.............. 83 QTAM ................................. 93 Data set control blocks formats 0, 1, 2, 3, 4, 5, 6 •••••••• 121 Da ta set labe 1 direct access storage (see data set control block) magnetic tape •••••••••••••••••••••• 145 label 1 (FL1) •••••••••••••••••••••• 147 label 2 (FL2) ....................... 151 DCB (see data control block) DD entry (see task input/output table) DEB (see data extent block) DEC (see data event control block) DECB (see data event control block) Destination queue block segment (see DASD message queue block segment) Device classes unit control block (UCBTYP field) ._ 265 d ••••••••••••••• CCHH (see MBBCCHHR) CCHH of defective track input/output block 173 Chained channel-program scheduling (see scheduling-dependent block segment) Checkpoint data set (QTAM) data control block ••••••••••••• n. 61,65 n •••••••••••••••• Q 0 • • • • • • • • • • • ... •• Index 281 Device-dependent block segments data control bloc k .......... 28,44,56, 79 data extent block ..................... 90 data set label •••.••••.....•... 121,145 input/output block ••••••••••••• ~ ••• 174 UCBTYP field ............................ 267 unit control block ••••••••••••••••• 259 Device entry (see task input/output table) Device name table •••• 155 Device optional path status unit control block .................... 259 Directory entry (see partitioned data set directory entry) DNT (see device names table) DSCB (s ee data set control block) DS1, DS2, DS3, DS4. DS5, DS6 (s ee data set control block) 0 •••••••••••••••• Error routine key unit control block 258 ECB (see event control block) Event control block ................ ., ••• 159 EXCP access method (see access method block segments) FLl (see data set label) FL2 (see data set label) Foundation extension, prefix data control block ....... 31,45,57,72,79 Foundation segment, before OPEN, after OPEN data control block ••• 32,46.57,65,73,79 (see also common block segments) GAM (see access method block segments) Graphic job processing communication vector table •••••••••• 18 task control block ••••••••••••• 244,245 JFC (see job file JFCB (see job file Job file control Job file control control block) control block) block •••••••••••••••• 177 block extension ....... 187 Label processing task input/output table •••••••••••• 251 LCB (see line control block) LERB (see line error block segment) Line control block •••••••••••••••••••• 189 Line control block segment data extent block ••••••••••••••••••• 98 Line DECB (see data event control block -- QTAM) Line error block segment line control block .............. 189,194 Line group block segment (extension, interface) data control block-QTAM ••••••• 61,64,67 LPRB (see request blocks (PCP, MFT» LRB (see request blocks (PCP, MFT» MBBCCHHR ................................. 7 Message queue block segment (see processing program message queue; DASD message queue) MFT ....................................... 7 MFT segments, field uses communication vector ta.ble •••••••••• 16 task control block ••••••••••••••••• 242 Multiprogramming with a fixed number of tasks (MFT) (see MFT) Multiprogramming with a variable number of tasks (MVT) (see MVT) MVT ........................................ 7 MVT segments, field uses communication vector table •••••••••• 16 ta sk control block ••••••••••••••.• '. • •• 242 Normal channel-program scheduling (see scheduling dependent block segment) HH (see MBBCCHHR) Partition information task control block ••••••••••••.•••• 246 Partitioned data set directory entry •• 195 ICB PCP •••••.•• ,•••••••••••••••••••••••.•••••• (see interruption control block) Input/output block ....................... Interruption control block ............. lOB (see input/output block) IQE flag IRB ................................. SIRB ••••••••••••••••••••••••••••••• IRB (see request blocks) PDS 282 as System Control Blocks 165 161 (see partitioned data set directory entry) Polling list origin block segment (see line group block segment entension) 220 227 PRB (see request blocks) Primary control program (see PCP) 7 ( Processing program message queue block segment (extension, interface) data control block ••••••••••••••• 65,67 data extent block ••••••••••••••••••• 93 PURGE (SVC16) - Quiesce count data extent block •• _ •••••••••••••••• 89 QISAM (see access method block segment) QSAM (see access method block segments) QTAM (see access method block segments) Queue control block segment data extent block ••••••••••••••••••• 96 RB (s ee request block (MVT» Receive scheduler sub-TCB block segment line control block ••••••••••••••••• Refreshable module PDS directory entry •••••••••••••••• request block •••••••••••••••••••••• Request blocks •••••••••••••••••••••••• MVT (IRB, PRB, SIRB, SVRB) ••••••••• PCP, MFT (IRB, LPRB, LRB, PRB, SIRB, SVRB) ••••••••••••••••••••••••••••• Rollout flags task control block ••••••••••••••••• 194 203 213 207 215 209 242 Shared DASD communication vector table •••••••••• 17 task control block ••••••••••••••••• 244 unit control block ••••••••••••• 261,269 Scheduling dependent block and segment input/output block ••• 172 interruption control block ••••••••• 161 Seek queue - UCB Deleted SIRB (see request blocks) SRT (see unit control block) Subroutine identification block segment data extent block ••••••••••••••••••• 92 SVRB (see request blocks) System resource table -- SRT (see unit control block) SYS1. LOGREC DCB •••••••••••••••• _ •••••••••••••••• 28 Tape volume serial number communication vector table •••••••••• 17 TCB (see task control block) TIOT (see task input/output table) Task control block •••••••••••••••••••• 239 Task input/output table ••••••••••••••• 249 Terminal models UCBTYP field ••••••••••••• '•••••••••• 266 Time-slicing communication vector table •••••••••• 19 task control block ••••••••••••••••• 242 UCB (see unit control block) UCBTYP field, detail description •••••• UCS segment job file control block ••••••••••••• unit control block ••••••••••••••••• Unit control block •••••••••••••••••••• User field communication vector table ••••••••• 265 184 259 253 d 17 VOL (see volume labe 1) Volume label •••••••••••••••••••••••••• 275 Volume label processing unit control block ••••••••••••••••• 262 Volume mount switch unit control block ••••••••••••••••• 262 Volume serial number communication vector table •••••••••• 17 Volume table of contents •••••••••••••• 211 relative address - UCB ••••••••••••• 262 VTOC (see volume table of contents) ft • • • • • • • • • • • • • Wi (see input/output block) XRB (see request block (PCP, MFT» 2260 UCBTYP field 281+8 UCBTYP field 2780 UCBTYP field 211 211 273 Index 283 ( C28-6628-3 International Business Machines Corporation Data Processing Division 112 East Post Road, White Plains, N.Y. 10601 [USA Only] IBM World Trade Corporation 821 United Nations Plaza, New York, New York 10017 [International] ( READER'S COMMENT FORM IBM System/360 Operating System System Control Blocks Form C28-6628-3 • Is the material: Easy to read? ................................................. ...................................... ... ....................................... 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