CICS - Group home

CICS VR - CHANGE ACCUMULATION

By Chitra Devi S posted Wed November 24, 2021 01:46 AM

  

CICS VSAM Recovery (CICS VR) is an automated recovery product. It recovers lost or physically damaged VSAM datasets that are updated by Batch and CICS applications. It provides forward recovery and backout for VSAM datasets.

CICS VR Forward Recovery

CICS VR forward recovery constructs a recovery job when VSAM data has been physically damaged or lost. The dataset can be a VSAM KSDS, ESDS, RRDS, or VRRDS.

The updates done to the VSAM dataset are recorded on an MVS system logger log stream as after image. When the VSAM dataset got any physical or logical corruption, CICS VR Forward recovery gets the information that it needs to construct the recovery job from the RCDS and using after image in the log and last backup, it recovers the VSAM dataset to its exact state before the data was lost.

CICS VR Change Accumulation

CICS VR Change accumulation (CA) is the process of consolidating forward recovery log records into a change accumulation dataset. CICS VR uses the change accumulation dataset in conjunction with the forward recovery log to speed up forward recovery processing.

CICS VR Change accumulation process reads the forward recovery log for a certain log range. Later it selects the log records for the spheres in that CA group that are important for the forward recovery and then calls DFSORT to sort these log records. CA saves the last update for each record using the sorted log records. Then it stores the consolidated records in the CA dataset.


Using the CA dataset and the recent backup of the VSAM, CICS VR performs recovery for the VSAM. By using the CA dataset, the time required to perform a forward recovery is reduced.

  1. Create a CA batch job to define CA groups and identify the spheres in the group.

Then run the CA batch job after a backup is taken for any of the spheres in the CA group or set up a CA batch job so that it is regularly submitted with a production planning system such as schedulers in.

  1. Recover the VSAM sphere. Using the ISPF panels to restore the backed-up version of the sphere and generate the necessary JCL using information from RCDS, the recovery will be done.

The APPLYCA keyword is generated on the RECOVER command.


Benefits of CA in CICS VR

Consider a VSAM dataset having huge data and updated continuously, on the occurrence of an error to perform FORWARD RECOVERY, CICS VR reads the log records. It takes time to read the entire log to find the recent after image.

By using the Change Accumulation process, the time required to perform Forward recovery for the frequently updated VSAM dataset is reduced.

For the VSAM dataset, which is not frequently updated, there is no need to use Change Accumulation.


0 comments
3 views