To prevent damage to a data set, DFSMStvs defers the decision whether
to back out a specific record to an installation exit, the batch override
exit. Transaction VSAM calls this optional exit when it backs out
a unit of recovery (UR) that involves a data set that might have been
impacted by the IDCAMS SHCDS PERMITNONRLSUPDATE command. The exit
is called once for each affected undo log record for the data set.
The purpose of this exit is to return to DFSMStvs with an indication
of whether or not the backout should be applied. The input is an undo
log record (mapped by IGWUNLR) and a data set name. The output is
a Boolean response of whether or not to do the backout, returned in
register 15:
- 0 (zero) means do not back out this record.
- 4 means back out this record.
The exit is given control in the following environment:
- INTERRUPTS enabled
- STATE and KEY problem program state, key 8
- ASC Mode P=H=S, RLS address space
- AMODE, RMODE: No restrictions
- LOCKS: None held
- The exit is reentrant