System Control Blocks

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Bytes and Offset Alignment 6 (6) . • 2 8 (8) 4 12 (C) 4 16 (10) 4 20 (14) 4 24 (18) 4 28 (lC) 4 Field Name Byte 2 1 ••• • 1 •• •• • x x ••• 0 ••• 1 ••• • x •• • 0 •• • 1 •• • • 1. •• 11 •• 01 •••• DECLNGTH DEC DCBAD DECAREA DEC IOBPT DECKYADR DECRECPT DECNA Byte 1 Bytes 2-4 DATA EVENT CONTROL BLOCK -- BDAM Field Description, Contents, Meaning 5 coded for key address. 5 coded for block length • Reserved • Type of operation - WRITE READ Type of search argument - Id • Key. Add option of WRITE operation • RU is suffixed to the type, indicating that the feedback address pointed to by DECNXADR can be the address of either the next data record or the next capacity record, whichever occurs first. R is suffixed to the type, indicating that the feedback address pointed to by DECNXADR is the address of the next data record. Length of the data. Address of the DCB to which this I/O request is related. Address of the data. Address of the lOB. Address of the key. Address of the block reference field. Reserved. 150 05 System Control Blocks (Release 21.1) Address of the next address feedback field. Present only if R or RU is coded in the READ macro.
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 13D shows the format of the DECB used in QTAM. Descriptions of the fields follow the illustration. DECB -- QTAM 151
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Systems Reference Library IBM Syste
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Figures Figure 1A. Pointer Diagram
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System Control Blocks System contro
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. ..J MFT Figure lA. Pointer Diagra
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Contents Directory Entry (MVT Only)
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20 OS System Control Blocks (Releas
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Offset -8 (-8) 2 Bytes and Field Al
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Offset 124 (7C) 4 128 (80) 4 132 (8
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0(0) 4 (4) 8 (8) 12 (c) 16 (10) 20
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DATA CONTROL BLOCK -- SAM Continued
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Offset 53 (35) • 3 56 (38) 1 57 (
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Device Interface 16 (10) Common Int
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Offset 16 (10) 1 11 (11) • 1 18 (
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Offset 40 (28) 8 48 (30) 1 49 (31)
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Offset Bytes and Field Alignment Na
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Device Interface 16 (10) Common Int
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WTTA Interface 16 (10) DCBBQFLG Dat
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Offset 20 (14) 1 21 (15) • 3 24 (
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Offset Bytes and Field Alignment N
Page 103: DATA CONTROL BLOCK -- TCAM The form
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Page 110 and 111: Offset 52 (34) 1 52 (34) 4 56 (38)
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Page 114: Appendage Table DATA EXTENT BLOCK -
Page 119 and 120: offset -36 (-24) 4 -32 (-20) 4 -28
Page 121 and 122: Offset Bytes and Field Alignment Na
Page 124: Offset +0 +0 +0 +1 +0 +4 +8 +0 +4 +
Page 127: DATA EXTENT BLOCK -- QTAM MESSAGE P
Page 131 and 132: Offset 48 (30) 4 52 (34) 1 53 (35)
Page 134 and 135: - 36 (- 24) -32 (-20) -28 (+ lC) -2
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Page 139 and 140: DATA EVENT CONTROL BLOCK -- BSAM Th
Page 141 and 142: Offset 12 (e) 4 16 (10) 4 20 (14) 4
Page 143 and 144: DATA EVENT CONTROL BLOCK -- BlSAM T
Page 148: o (0) DATA EVENT CONTROL BLOCK -- B
Page 153 and 154: DATA EVENT CONTROL BLOCK -- BTAM Th
Page 157 and 158: Offset Bytes and Field Alignment Na
Page 159 and 160: Offset 28 (lC) 29 (lD) • 1 Bytes
Page 161: Device Name Table The device name t
Page 166 and 167: 166 05 System Control Blocks (Relea
Page 168: 10 (0) ....,r- 44 (2C) DS1FMTID For
Page 177 and 178: 72 (48) FORMAT 2 -- INDEX DATA SET
Page 179 and 180: Offset 64 (40) 2 Bytes and Alignmen
Page 181 and 182: FORMAT 3 -- EXTENSION DATA SET CONT
Page 185 and 186: Offset o (OJ 44 44 (2C) 1 45 (2D)
Page 188: ...... ---r 0(0) 4 (4) 44 (2C) DS5F
Page 191 and 192: FORMAT 6 -- SHARED EXTENT DATA SET
Page 193 and 194: Data Set Labels -- Magnetic Tape Th
Page 196 and 197: o (0) :.::: 4 (4) .,r- Continued Co
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0(0) 4 (4) 16 (10) 36 (24) FL2RECFM
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Event Control Block The event contr
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INTERRUPTION CONTROL BLOCR 0(0) ICB
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Input/Output Block The input/output
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Offset 68 (44) 1 70 (46) •• 2 7
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Offset 101 (65) • 1 101 (65) •
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236 OS System Control Blocks (Relea
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JOB STEP CONTROL BLOCK 240 (FO) JSC
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240 os System Control Blocks (Relea
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Offset 40 (28) 2 40 (28) 41 (29) 42
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Offset 96 (60) 1 91 (61) • 3 100
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Offset I o (0) 8 8 (8) 3 *tes and ,
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Offset Bytes and Alignment I 24 (18
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Offset Bytes and Field A1ignment Na
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REQUEST BLOCKS -- MVT CONFIGURATION
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Interruption Request Block -- MVT T
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proqram Request Block -- MVT The pr
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Offset o (0) B 8 (8) 1 9 (9) • 1
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Supervisor Request Blocks -- MVT Th
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Supervisor Request Block -- MVT --
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SUPERVISOR REQUEST BLOCK -- MVT --
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302 OS system Control Blocks (Relea
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Offset o 1 2 4 8 (0) 1 Bytes and Fi
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Bytes and Offset Alignment 105 (69)
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1-32 (20) r- L,. 0(0) 4 (4) 8 (8) 1
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Bytes and Field Offset Alignment Na
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1116 (74) 120 (78) 124 (7C) 128 (80
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Offset 31 (IF) 32 (20) Byte and Fie
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Offset 168 (AB) 4 172 (AC) 1 173 (A
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TIMING CONTROL TABLE 0(0) TCTQA 3 (
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Offset o (0) 3 Bytes and Field Alig
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Offset o 4 6 8 10 +0 (0) 4 (4) 2 By
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Offset +3 +4 +12 +15 +0 Bytes and F
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UCS 1403 Printer Extension 0(0) 4 (
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Offset 45 (2D) • 3 48 (30) 8 56 (
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Offset Bytes and Alignment 10 (A)
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MAGNETIC TAPE DEVICE CLASS UCBTYP B
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Byte 1 lOS Flogs I Model Code I UCB
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UCB + 16 (10) Offset 16 (10) 1 Byte
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ASCII Volume Header Label I 0 (0) 1
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Volume Table of Contents The volume
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Volume Table of Contents The volume
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Time-Sharing Option Control Blocks
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Driver Parameter Area The driver pa
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ENVIRONMENT CONTROL TABLE 0(0) ECTR
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Protected Step Control Block The pr
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Offset o (0) 7 Byte and Field Align
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Time-Sharing Job Block The time sha
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Indexes to system reference library
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liO coo.nter table 339 I/O lookup t
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System Control Blocks

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