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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.
Recoverable resources
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:
v CICS files that relate to:
– VSAM data sets
– BDAM data sets
v Data tables (but user-maintained data tables are not recovered after a CICS
failure, only after a transaction failure)
v Coupling facility data tables
v The CICS system definition (CSD) file
v Intrapartition transient data destinations
v Auxiliary temporary storage queues
v Resource definitions dynamically installed using resource definition online
(RDO)
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 a
concurrent copy capability. This capability enables you to 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 (CICSVR), to recover the VSAM file.
CICS backward recovery (backout)
Backward recovery, or backout, is a way of undoing changes made to resources
such as files or databases.
Backout is one of the fundamental recovery mechanisms of CICS. It relies on
recovery information recorded while CICS and its transactions are running
normally.
Before a change is made to a resource, the recovery information for backout, in the
form of a before-image, is recorded on the CICS system log. A before-image is a
record of what the resource was like before the change. These before-images are
used by CICS to perform backout in two situations:
v In the event of failure of an individual in-flight transaction, which CICS backs
out dynamically at the time of failure (dynamic transaction backout)
Chapter 1. Recovery and restart facilities 5