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VTAPE_CDS_SEPARATION

Description

On different DASD volumes, allocate the Global VCAT, BSDS, and ICF Catalog data sets that CA Vtape uses. Allocate any combination of the data sets on the same volume to create a single point of failure, inhibit disaster recovery, but degrade performance due to contention.

Best Practice

The CA Vtape control data sets are critical system files. Keep these files on high-performance reliable media, such as a RAID-compliant DASD, to improve performance and minimize potential system outages. CA Vtape uses Hardware Reserve processing to serialize access to the Global VCAT. The need to perform volume Hardware Reserve may require you to isolate the Global VCAT on a single DASD volume. To ensure recoverability if the hardware unexpectedly fails, maintain current backups of the BSDS and keep the Global VCAT and BSDS on separate DASD volumes.

Allocating the ICF Catalog that CA Vtape uses or any other ICF catalog on the same DASD volume with the Global VCAT or the BSDS causes contention on the concurrent data set volume. This contention degrades performance and could lead to lock outs when other software products that scan catalogs or VTOCs are active in your environment.

We recommend that you relocate all CA Vtape control data sets to separate, high performance, RAID-compliant DASD volumes. Also allocate the CA Vtape control data sets in separate DASD subsystems. The allocation spreads the workload across separate channels and control units. The allocation maximizes performance, recovery, and availability.

Parameters Accepted

None

Debug Support

Yes

Verbose Support

Yes

Reference

For more information pertaining to the DASD placement and recovery of CA Vtape control data sets, see the chapters "Operational Considerations" in the Configuration Guide and "Recovering CA Vtape" in this guide.

Messages

SVTH1251E

A combination of the CA Vtape control data sets has been allocated on the same DASD volume. This is a single point of failure and could also degrade performance due to contention.