DFSMShsm: Stop using the HOLD command to quiesce activity prior to control data set backup

Description: Before z/OS® V1R13, you might have manually or programmatically held DFSMShsm activity using the HOLD command prior to starting a control data set (CDS) backup. Starting with z/OS V1R13, the ARCCAT resource is released by all functions running on z/OS V1R13 DFSMShsm hosts, and the functions are quiesced when CDS backup starts. Manually or programmatically holding DFSMShsm activity is no longer necessary.

Element or feature:

DFSMShsm.

When change was introduced:

z/OS V1R13.

Applies to migration from:

z/OS V1R12.

Timing:

Before the first IPL of z/OS V2R1.

Is the migration action required?

No, but recommended because DFSMShsm will automatically release the ARCCAT resource when a CDS backup is starts.

Target system hardware requirements:

Cross coupling facility (XCF) services are required to communicate the start of a CDS backup to all DFSMShsm hosts. XCF services must be available and configured properly.

Target system software requirements:

None.

Other system (coexistence or fallback) requirements:

None.

Restrictions:

The following are restrictions of taking this migration action.

In a record-level sharing (RLS) CDS environment, all DFSMShsm hosts in the HSMPlex must be z/OS V1R13 or later hosts.
In a non-RLS CDS environment, this migration action can be taken on z/OS V1R13 DFSMShsm hosts without changing hosts running on prior releases of z/OS.
Some DFSMShsm environment configuration do not require XCF services. Specifically, a non-RLS CDS non-multiple address space DFSMShsm (MASH) configuration typically does not require XCF services. However, XCF services are required and must be available and configured in all DFSMShsm RLS CDS and MASH configurations.

System impacts:

If you continue to issue a HOLD command to quiesce DFSMShsm activity before a CDS backup and a corresponding RELEASE command to resume activity after CDS backup is complete, the only impact is that you will not see the performance benefit intended by this enhancement.

Related IBM® Health Checker for z/OS check:

None.

Steps to take: On all z/OS V2R1 DFSMShsm hosts:

Remove the procedures, processes, or programs that issue the HOLD command to quiesce DFSMShsm activity prior to starting CDS backup.
Remove the corresponding procedures, processes, or programs that issue the RELEASE command to resume DFSMShsm activity after CDS backup completes.

Reference information: For an overview of the CDS backup enhancement that relieves ARCCAT resource contention, see z/OS DFSMS Using the New Functions