System Control Blocks

Offset
50 (32) •• 2
50 (32)
51 (33)
50 (32)
51 (33)
40 (28) 2
42 (2A) •• 2
44 (2C) 1
45 (2D) • 3
48 (30) 1
Bytes and Field
Alignment Name
DCBMACR
Byte 1
00.0 0 •••
•• 1.
• 1 ••
• .1.
••• x
Byte 2
00.0 0000
· .1.
Byte 1
0.0 •• 0 ••
• 1 •.
· .. 1 1 •••
• .xx
Byte 2
1 •••
.1 ..
• .0.
· •• 1 1 •..
.1 ••
· .1.
••• 1
DCBTIOT
DCBMACRF
DCBIFLGS
DCBDEBAD
DCBOFLGS
DATA CONTROL BLOCK -- ISAM
Hex.
Dig. Field Description, Contents, Meaning
FOUNDATION SEGMENT -- BEFORE OPEN (Continued)
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.
R
S
C
w
G
M
L
S
P
M
L
U
K
I
BISAM
Always zero for BISAM.
READ
Dynamic buffering •
CHECK
(Reserved bit)
BISAM
Always zero for BISAM.
WRITE
QISAM
Always zero for QISAM •
GET
Move mode of GET.
Locate mode for GET.
(Reserved bits)
QISAM
SETL
PUT or PUTX.
Always zero for QISAM.
Move mode of PUT.
Locate mode of PUT.
Update in place (PUTX).
SETL ty key.
SETL by ID •
FOUNDATION SEGMENT -- AFTER OPEN
A two byte field containing the offset from the TrOT
or1g1n to the TIOELNGH field in the TIOT entry for
the DD state..ment associated with this DeB"
Contents and meaning are the same as those of the
DCBMACR field in the foundation before OPEN.
Contents and meanings are the same as those of the
DCBIFLG field in the foundation before OPEN.
Address of the associated DEB.
Note: The above fields overlay the DCBDDNAM field
during OPEN and are restored to their original form
at CLOSE.
Contents and meanings are the same as those of the
DCBOFLGS field in the foundation before OPEN.
DCB -- ISAM 69