System Control Blocks

Offset
48 (30) 4
52 (34) 1
53 (35) • 3
56 (38) 1
51 (39) • 3
60 (3C) 1
61 (3D) • 3
64 (40) 2
Bytes and
Alignment
66 (42) •• 22
-16 (-10) 1
-15 (-F) • 1
-8 (-8) 4
-4 (-4) 1
-3 (-3; • 3
o (O) 1
1 (1) • 3
4 (4) 1
5 (5) . 3
8 (8) 13
21 (15) • 3
24 (18) 1
25 (19) • 3
28 (lC) 4
DATA EXTENT BLOCK -- QTAM
Field Description, Contents, Meaning
BUFFER REQUEST BLOCK
Reserved.
Priority.
Reserved.
X'08'; identifies the operation code for a TIC command.
Address of the process queue control block on the direct access
device.
X'01'; indicates a dummy buffer request block.
Address of the beginning of the line control block portion of this
DEB.
END OF BUFFER REQUEST BLOCK
Size of work area necessary for GET.
Reserved.
PREFIX
DESTINATION QUEUE
Work area used by I/O support routines.
Direct access device address used by I/O support routines. Format
(BBCCHHR)
DCB modification mask used by I/O support routines.
Length of this DEB.
Reserved.
BASIC SECTION
Reserved.
Address of TCB.
Reserved.
DEB PROPER
Address of the next DEB in the same task.
Reserved.
Address of the next DEB on the chain of processing program's DEBs.
X'OF' identifies this block as a DEB.
Address of the DCB.
Reserved.
DEB -- QTAM 131