System Control Blocks

Offset
Bytes and Field
Alignment Name
DATA CONTROL BLOCK -- BDAM
32 (20) 1 DCBHIARC, DCBBFTEK, DCBBFALN
(continued)
33 (21) • 3
36 (24) 1
37 (25) • 3
40 (28) 8
48 (30) 1
• .xx
• .10
•• 01
• .11
.x.x x •••
DCBRECFM
10 ••
01 ••
11 ••
.. 1.
• •• 1 1 •••
• 00.
••• 1
DCBEXLST
DCBDDNAM
DCBOFLGS
1 ••.
• x.. • x •.
• .0. 0 ••••
••• 1
• .0.
• .1.
... 1
Field Description, Contents, Meaning
FOUNDATION EXTENSION (Continued)
D
F
F
Reserved.
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 bits)
Record format.
Code
F
V
U
T
B
S
Fixed record length.
Variable record length.
Undefined record length.
Track overflow •
Blocked (allowed only with V).
Spanned (allowed only with V).
Always zeros •
Key length (KEYLEN) was specified in the DCB
macro instruction. This bit is inspected by
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
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.
Flags used by the OPEN routine.
The data set is being opened for INPUT 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 .Q 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.
the
DCB -- BDAM 79