ABCs of z/OS System Programming Volume 3 - IBM Redbooks

7.12 The batch window problem
Batch window - a period of time in which CICS
access to recoverable data sets is quiesced so
batch jobs can run
Requires taking a backup of the data set
Batch updates are then performed
A forward recovery backup is taken, if needed
When finished, CICS access to the data set is
re-enabled
Figure 7-12 Batch window problem
Batch window
The batch window is a period of time in which online access to recoverable data sets must be
disabled. During this time, no transaction processing can be done. This is normally done
because it is necessary to run batch jobs or other utilities that do not properly support
recoverable data, even if those utilities use also RLS access. Therefore, to allow these jobs or
utilities to safely update the data, it is first necessary to make a copy of the data. In the event
that the batch job or utility fails or encounters an error, this copy can be safely restored and
online access can be re-enabled. If the batch job completes successfully, the updated copy of
the data set can be safely used because only the batch job had access to the data while it
was being updated. Therefore, the data cannot have been corrupted by interference from
online transaction processing.
Quiescing a data set from RLS processing
Before updating a recoverable data set in non-RLS mode, quiesce the data set around the
sysplex. This is to ensure that no RLS access can be done while non-RLS applications are
updating those data sets. The quiesced state is stored in the ICF catalog. After a quiesce has
completed, all CICS files associated with the data set are closed. A quiesced data set can be
opened in non-RLS mode only if no retained locks are presented. Once the data set was
quiesced from RLS processing, it can be opened again in RLS mode only after it is
unquiesced.
See 7.20, “Interacting with VSAM RLS” on page 412 for information about how to quiesce and
unquiesce a data set.
Chapter 7. DFSMS Transactional VSAM Services 395