The CICS® recovery manager provides the recovery and restart functions needed in an online system.
Automatic backout is provided for most CICS resources (such as databases, files, and auxiliary temporary storage queues), either following a transaction failure or during an emergency restart of CICS. The logging functions necessary to support backout are performed for you by the CICS recovery manager and the log manager. If the backout of a VSAM file fails, CICS backout failure processing ensures that all locks on the backout-failed records are retained, and the backout-failed parts of the unit of work (UOW) are shunted to await retry. The VSAM file remains open for use. (For an explanation of shunted units of work and retained locks, see The shunted state.)
If the cause of the backout failure is a physically damaged data set, and provided the damage affects only a localized section of the data set, you can choose a time when it is convenient to take the data set offline for recovery. You can then use the forward recovery log with a forward recovery utility, such as CICSVR, to restore the data set and re-enable it for CICS use.
You don't need to shut CICS down to perform these recovery operations. For data sets accessed by CICS in VSAM record-level sharing (RLS) mode, you can quiesce the data set to allow you to perform the forward recovery offline. On completion of forward recovery, setting the data set to unquiesced causes CICS to perform the backward recovery automatically.
For files accessed in non-RLS mode, you can issue an EXEC CICS or CEMT SET DSNAME RETRY after the forward recovery, which causes CICS to perform the backward recovery online.
Another way is to shut down CICS with an immediate shutdown and perform the forward recovery, after which a CICS emergency restart performs the backward recovery.
In CICS, a recoverable resource is any resource with recorded recovery information that can be recovered by backout.
The following resources can be made recoverable:
In some environments, a VSAM file managed by CICS file control might need to remain online and open for update for extended periods. You can use a backup manager, such as DFSMSdss™, in a separate job under MVS™, to back up a VSAM file at regular intervals while it is open for update by CICS applications. This operation is known as backup-while-open (BWO). Even changes made to the VSAM file while the backup is in progress are recorded.
DFSMSdss is a functional component of DFSMS/MVS®, and is the primary data mover. When used with supporting hardware, DFSMSdss also provides concurrent copy capability. Concurrent copy lets you copy or back up data while that data is being used.
If a data set failure occurs, you can use a backup of the data set and a forward recovery utility, such as CICS VSAM Recovery MVS/ESA™ (CICSVR), to recover the VSAM file.
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