Defining coupling facility cache structures and cache sets

VSAM RLS support requires the coupling facility to define cache structures for cross-system buffer invalidation. You determine the number and size of cache structures you require.

The number you require depends on factors such as these:
  • The number of coupling facilities you have
  • The amount of space in each coupling facility
  • The amount of data that is accessed through each coupling facility

See the z/OS DFSMSdfp Storage Administration Reference manual for information about calculating the amount of space you require for the cache structures. If you have previously used data sets in LSR mode, the total amount of coupling facility space allocated to cache structures will not be less than the amount of storage you were using for LSR pools, including any hiperspace buffers.

To achieve performance benefits:
  • Make the size of the cache larger
  • Divide cache structures appropriately across coupling facilities

You define cache structures in the CFRM policy with the IXCMIAPU utility.

Defining cache sets

You define cache sets with the ISMF control data set (CDS) application. A cache set maps onto one or more cache structures. If you specify more than one cache set, the data sets can be rebound to another cache structure in the set if a cache structure fails.

See the z/OS DFSMSdfp Storage Administration Reference manual for more information about cache sets.