IBM SC34-7012-01 - Manual (Page 225)

Shutdown and restart
The way CICS closes files is determined by whether the shutdown is controlled,
immediate, or uncontrolled.
Controlled shutdown
During a controlled shutdown, CICS closes all open files defined in the FCT. This
ensures that, for files that are open for update and eligible for BWO, the BWO
attributes in the ICF catalog are set to a ‘BWO disabled’ state
If a failure occurs during shutdown so that CICS is unable to close a file, CICS
issues warning message DFHFC5804. In this case, check the BWO attributes and, if
necessary, either use DFSMSdfp IGWABWO callable service to set the attributes, or
discard any BWO backups that are taken in the batch window that follows the
shutdown.
Immediate or uncontrolled shutdown
During an immediate or uncontrolled shutdown, CICS does not close the files
defined in the FCT, and so the BWO attributes in the ICF catalog are not updated.
Use the DFSMSdfp IGWABWO callable service to set the attributes (see “An
assembler program that calls DFSMS callable services” on page 218 for an example
of how to do this). Do not run any batch jobs before the next CICS restart. If you
do, for releases prior to DFSMS 1.2, discard any BWO backups that are taken in
the batch window.
For DFSMS 1.2 onward, the controls in DFSMS allow DFSMSdss to detect a backup
that is invalidated if CICS applications are shut down (normally or abnormally)
and if batch programs are executed that update the data set while the BWO
backup is in progress. This allows DFSMSdss to discard the backup, which
prevents DFSMShsm from erroneously discarding the oldest valid backup from the
inventory maintained by DFSMShsm.
Restart
At the next CICS restart, the following BWO-dependent actions can occur when a
data set is opened for update:
v If the BWO attributes in the ICF catalog are set to the ‘BWO enabled’ state, CICS
issues warning message DFHFC5808.
v If the file has been redefined as BACKUPTYPE(STATIC), and:
– CICS has been cold started
– The original base cluster DSNB has been discarded
– The BWO attributes in the ICF catalog are set to the ‘BWO enabled’ state
CICS issues warning message DFHFC5809.
v If the file has been redefined as BACKUPTYPE(STATIC), and:
– CICS has been warm or emergency restarted
– The original base cluster DSNB has been kept
CICS fails the file-open operation with message DFHFC5807.
Data set backup and restore
BWO backups are taken at the VSAM sphere level. You can use DFSMShsm or
DFSMSdss to take the backup copy. You are recommended to use DFSMShsm
because, without DFSMShsm installed, you must supply automatic class selection
(ACS) routines to fulfil the SMS requirements for BWO support.
Chapter 18. Backup-while-open (BWO) 213