CICS® VR
change accumulation (CA) is the process of consolidating forward recovery
log records into a change accumulation data set. CICS VR uses the change accumulation data
set in conjunction with the forward recovery log to speed up forward recovery
processing.
Change accumulation is a two step process:
- You must first create CA batch jobs that define CA groups and identify
the spheres that are in each group. When you run one of these CA batch jobs,
CA reads the forward recovery log for a certain log range, selects the log
records for the spheres in that CA group that are important for 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 CA stores the consolidated records in the CA data
set. Every time you run the CA batch job, the change accumulation data set
is updated with the information from the next log range. You must perform
the following:
- Run the CA batch job after a backup is taken for any of the spheres in
the CA group.
- Set up a CA batch job so that it is regularly submitted with
a production planning system, such as Tivoli® Workload Scheduler for z/OS®.
CA runs in parallel with CICS production runs or VSAM batch logging;
so keeping the CA data set as current as possible reduces the amount of log
data that must be read and applied to forward recover a VSAM sphere.
- The second step occurs when you want to forward recover a VSAM sphere.
Use the ISPF panels to restore the backed up version of the sphere and generate
the necessary JCL using information in the CICS VR RCDS. The APPLYCA keyword is generated
on the RECOVER command. APPLYCA tells CICS VR to apply the records in the CA
data set to the restored VSAM sphere, and then to apply the remaining log
range from the forward recovery log to pick up the most recent changes.