IBM SC34-7012-01 manual What can prevent a switch to non-RLS access mode?

Note: If your file definitions specify an LSR pool id that is built dynamically by CICS, consider using the RLSTOLSR system initialization parameter.

vOpen the files non-RLS read-only mode in CICS.

vConcurrently, run batch non-RLS.

vWhen batch work is finished:

–Close the read-only non-RLS mode files in CICS.

–Re-define the files as RLS mode and with update operations. You can do this using the CEMT, or EXEC CICS, SET FILE command.

–Unquiesce the data sets.

–Open the files in CICS, if not using open on first reference.

–Resume normal running.

You should also take data set copies for recovery purposes before and after a batch run as you would normally, regardless of whether you are switching from RLS to non-RLS access mode.

What can prevent a switch to non-RLS access mode?

You cannot open a data set in non-RLS access mode if there are any ACBs open against it in RLS access mode.

To switch from RLS to non-RLS access mode, first ensure that all files that are open against the data set are closed. You can use the quiesce function for this purpose. As discussed in “Quiescing RLS data sets” on page 167, the VSAM RLS quiesce mechanism causes each CICS region in the sysplex to close any RLS ACBs that are open against a specified data set. Once closed under the quiesce mechanism, data sets can only be opened in non-RLS mode. To re-enable quiesced data sets to be reopened in RLS mode, all open non-RLS ACBs must be closed and then the data sets must be unquiesced.

The quiesce mechanism cannot inform batch programs that have the data set open in RLS access mode about the quiesce request. If you have such programs, use the access method services SHCDS LIST subcommand to check whether any non-CICS jobs have ACBs open in RLS mode against the data set. For information about the SHCDS LIST subcommand, see z/OS DFSMS: Access Method Services for ICF.

Quiescing a data set sets the quiesce flag in the ICF catalog so that the data set can be opened in non-RLS mode only. This way of making data sets available for batch programs without having to shut down all the CICS regions is particularly suited to the Parallel Sysplex environment. Note that if you do shut CICS regions down, it is best to avoid immediate shutdowns when you have not specified a shutdown transaction, because this could cause large numbers of locks to be retained. A shutdown transaction can enable you to perform a quick but controlled shutdown.

Even if a data set has been quiesced, you still cannot open it for update in non-RLS access mode if SMSVSAM is holding retained locks against the data set. This is because the locks are needed to preserve data integrity: they protect changes that are waiting to be either committed or backed out. It is possible to open a data set for input (read-only) in non-RLS mode even when there are retained locks, because a reader cannot corrupt the data integrity that such locks are preserving. Note that, when you are opening a data set in a batch job, there cannot be any active locks because, when an ACB is closed, any active locks are converted automatically into retained locks.

Chapter 15. Resolving retained locks on recoverable resources 173