It is important to consider the differences between CICS® Transaction Server and earlier releases of CICS when planning for off-site recovery.
Support during emergency restarts for units-of-work that failed in-doubt or failed during backout is provided by the CICS recovery manager. This support is available at the remote site only if the system log is transmitted and the CICS regions at the remote site are running under CICS Transaction Server.
It is possible for system log records to be transmitted to the remote site for units-of-work that subsequently become indoubt-failed or backout-failed. The log records for failed units of work could be moved to the secondary log stream at the local site. However, resource managers such as RRDF are aware of such movements and act accordingly.
CICS provides support for remote site recovery where VSAM data sets are used in RLS mode at the primary site. Using this RLS support for remote recovery, you can switch over to the remote site without suffering indeterminate or unreported loss of data integrity.
If a disaster occurs at the primary site, your disaster recovery procedures should include recovery of VSAM data sets at the designated remote recovery site. You can then emergency restart the CICS regions at the remote site so that they can backout any uncommitted data. Special support is needed for RLS because record locks, which were protecting uncommitted data from being updated by other transactions at the primary site, are not present at the remote site. You invoke CICS RLS support for off-site recovery using the OFFSITE system initialization parameter.
The OFFSITE system initialization parameter protects all RLS data sets until all emergency restart recovery is complete. You can specify this OFFSITE system initialization parameter at run-time only--it cannot be specified and assembled in the SIT--and it is valid only when START=AUTO is specified. You specify OFFSITE=YES when restarting CICS regions at a remote site when recovery involves VSAM data sets opened in RLS mode.
When you specify OFFSITE=YES, file control performs RLS off-site recovery processing, under which file control does not allow any new RLS access during startup. With RLS recovery in operation during an emergency restart, CICS does not allow any data sets to be accessed in RLS mode until:
Operators should reply to the message only when all the CICS regions being restarted with OFFSITE=YES have issued the message, indicating that they have all completed their RLS recovery.
A CICS-supplied sample NetView® EXEC, DFH$OFAR, is provided to automate the detection of, and reply to, the WTOR console messages. For more information, see the prolog in the source member of the CICSTS31.CICSSDFHSAMP. library.
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