System Control Blocks

Offset
Bytes and Field
Alignment Name
14 (E) •• 1 DEBFLGSl
1. •• • •••
15 (F) ••• 1
.1 ..
• 1 ••
•• xx x. xx
16 (10) 1 DEBNMEXT
17 (11) • 3 DEBUSRPG
20 (14) 1 DEBPRIOR
21 (15) • 3 DEBECBAD
24 (18) 1 DEBPROTG, DEBDEBID
25 (19) • 3
28 (lC) 1
29 (10) • 3
32 (20) 1
33 (21) • 3
32 (20) 1
33 (21) • 3
36 (24) 4
31 (25) • 3
40 (28) 4
xxxx 1111
DEBDCBAD
DEBEXSCL
DEBAPPAD
DEBDVMOD
DEBUCBAD
DEBDVMOD
DEBUCBAD
DEBRDCB
DEBRDCBA
DEBPDCB
DATA EXTENT BLOCK -- ORDINARY
Field Description, Contents, Meaning
BASIC SECTION (Continued)
A flag field.
password was supplied during open processing. EOV
will not request a password for each additional
volume of a multivolume data set.
Set by EOV to inform CLOSE that an end-of-file has
been encountered and, therefore, deferred user label
processing is allowed.
EOV processing occurred during CLOSE processing •
Tested and set to zero by CLOSE; set to one by EOV.
(Reserved bits)
Reserved.
Number of extents specified in the DSCBS.
Address of first lOB in the user purge chain.
priority of the task.
Address of a parameter list used to locate the purge
ECB for an SVC purge request.
Protection key.
A hex wF- to identify this block as a DEB.
Address of DCB associated with this DEB.
Extent scale: 4 for direct access device and 2 for
non direct access device and communication device.
This field is used to deter.mine the size of the
device dependent section.
Address of the I/O appendage vector table.
DEVICE DEPENDENT SECTION
UNIT RECORD (EXCEPT 3505/3525) AND MAGNETIC TAPE
Device modifier.
Magnetic tape -- SET MODE operation code.
Unit record -- Not used.
Address of a UCB associated with a given data set.
IBM 3525 CARD PUNCH
Device modifier.
Magnetic tape -- SET MODE operation code.
Unit record -- Not used.
Address of a UCB associated with a given data set.
The address of the DCB for the READ associated data
set.
DEB 121