IBM SC33-1683-02 - Manual (Page 152)

When invoked
Whenever CICS is about to ignore a UOW log record that is due to be
backed out, because the lock that protected the updated record could have
been overridden by a non-RLS batch program.
Exit-specific parameters
UEPOLOGR
Address of the file control portion of a shunted log record that
represents an update to a data set for which retained locks may
have been overridden. The file control portion of the log record can
be mapped using the DSECT DFHFCLGD.
UEPODSN
Address of a 44-byte area of storage containing the name of the
data set whose locks were overridden.
Return codes
UERCNORM
Do not perform the backout of this log record. Any updates
performed by the batch run should take precedence.
UERCBCKO
Perform the backout. It is known that the actions of the batch job
could not have affected this update.
A return code of UERCPURG is not allowed. There is no need to set a
UERCPURG return code, because this global user exit is invoked during
syncpoint phase 2, and therefore cannot get a purged response from any
calls that it makes.
XPI calls
All can be used, but subject to the same caution as for API and SPI calls.
API and SPI calls
Although this exit is allowed to issue API and SPI calls, you should be very
careful about which commands you use because the exit is invoked during
file backout, which is part of syncpoint phase 2.
It is recommended that you restrict EXEC CICS commands to inquiries, and
avoid commands that update CICS resources, because the resources may
themselves be in a state of recovery. In particular, the following restrictions
apply:
1. Do not issue any recoverable operations.
2. Do not use operations that access systems or resource owners external
to this CICS, even if the target resource is non-recoverable.
3. Do not disable or close files, because this could cause further error
conditions.
4. It is possible for this exit to be invoked under a different transaction
environment from that under which the updates that are being backed
out were originally made. If your exit program wants to perform any
actions (such as writing a message to the terminal) that require it to be
running under the original transaction environment, it must first check
the value returned in the RE_ATTACHED_TRANSACTION parameter of
a transaction manager INQUIRE_TRANSACTION XPI call.
file control recovery program exits
120 CICS TS for OS/390: CICS Customization Guide