Changing the size of coupling facility cache structures

DFSMS uses the initial structure size specified in the CFRM policy each time it connects to a CF cache structure. In each case, the ALTER(YES) keyword is specified, indicating to MVS that this structure can be dynamically reconfigured. To alter the size of a CF cache structure, issue the SETXCF START command, using the following format:

   SETXCF START,ALTER,STRNAME=CF_cache_structure_name,SIZE=newsize

where:

CF_cache_structure_name: Is the name of the cache structure being altered.
newsize: Is the new structure size in megabytes.
This new size can be larger or smaller than the size of the current CF cache structure, but it cannot be larger than the maximum size specified in the CFRM policy.

MVS automatically starts the alter process in place, without disruptions to the application using the CF cache structure. The alter function does not cross CF boundaries and does not take the place of the rebuild function. If you require a larger structure size than that specified in the CFRM policy, you must activate a new CFRM policy and rebuild the structure. The alter function changes the cache structure in place; you can use the rebuild function to move a cache structure to another CF. See Defining CF cache structures for information on estimating the size of CF cache structures.