IBM SC34-7012-01 manual Resolving retained locks on recoverable resources, Quiescing RLS data sets

Chapter 15. Resolving retained locks on recoverable resources

This section describes how you can locate and resolve retained locks that are preventing access to resources, either by CICS transactions or by batch jobs.

About this task

Although the main emphasis in this section is on how you can switch from RLS to non-RLS access mode in preparation for batch operations involving the use of RLS-accessed data sets, it is also of interest for CICS online operation. It covers the following topics:

v“Quiescing RLS data sets”

v“Switching from RLS to non-RLS access mode” on page 172

v“Coupling facility data table retained locks” on page 182

Quiescing RLS data sets

Data sets opened by CICS in RLS mode can also be accessed by batch programs, provided the batch programs open them in RLS mode for read-only processing.

About this task

Batch programs cannot update recoverable data sets in RLS mode, because SMSVSAM prevents it. Thus, to update a recoverable data set from a batch program, first ensure that the data set is closed to all CICS regions. This allows the batch program to open the data set in non-RLS mode for update. (See “Switching from RLS to non-RLS access mode” on page 172.) To enable batch programs to access data sets opened in RLS mode, CICS supports the VSAM RLS data set quiesce and unquiesce functions.

The quiesce function enables you, with a single command, to close in an orderly manner throughout the sysplex any data sets that are open in RLS mode, and prevent the data sets being opened in RLS mode while they are in the quiesced state. This function is required in the data sharing environment because many CICS regions can have the same data set open for update at the same time. You can use the quiesce function to take a data set offline throughout the sysplex when:

vYou want to switch between RLS and non-RLS VSAM access modes.

vYou want to prevent data set access during forward recovery.

CICS supports the VSAM RLS quiesce interface by providing an RLS quiesce exit program that is driven for the quiesce and unquiesce functions. CICS regions initiating quiesce and unquiesce requests propagate these to other CICS regions, through the SMSVSAM control ACB and the CICS RLS quiesce exit program.

Other products such as DFSMSdss and CICSVR also communicate with CICS through their SMSVSAM control ACBs and the RLS quiesce exit.

© Copyright IBM Corp. 1982, 2010 167