CICS® VR VSAM batch logging provides logging for your batch changes to VSAM data sets that are not accessed in RLS-mode.
CICS VR forward recovery logging records an after-image log record for every update made to the VSAM data set by a batch job. Therefore allowing you to run CICS VR forward recovery to recover the batch updates if the data set becomes corrupted.
CICSVR undo logging records a copy of the data prior
to any changes being made, so UNDO logging is always done when any
indication is given of intent to update the data, therefore allowing
you to run CICSVR batch backout to remove the batch updates if the
batch job encounter an abend.
If a batch job reads all records using GET UPD commands
even though only a few records are actually updated, CICSVR undo logger
will record every before-image record. However unless a record is
updated, logging the before image is not necessary and it adds to
the overhead and runtime of the batch job. Also batch backout will
take longer when before-images are written back to a dataset but they
only replace identical records.
This unnecessary overhead could be avoided if the
application were rewritten to use GET commands instead of GET UPD
commands, and only use GET UPD commands when there is a definite intent
to UPDATE a record. The alternate approach to avoid such overhead
is to install the CICSVR APAR PM02913 and specify FRLOG(ALL) for the
sphere.
At VSAM batch logging with the FRLOG(ALL) parameter
UNDO logging occurs for GET for UPDATE commands and if a subsequent
PUT_UPDATE or ERASE is not done, CICS VR
will remove the GET for UPDATE UNDO record if it is still present
in the log buffer.