When you create CFRM policy specify your INITSIZE parameter equal to the SIZE parameter (SIZE=INITSIZE) for the structure. Remember the number of lock entries cannot be altered.

When the first system joins the star, global resource serialization uses information about the structure size specified in the CFRM policy and then creates the largest lock structure that will fit within that size. Message ISG3371I is issued to document the size of the structure. If the size of the ISGLOCK lock structure created by global resource serialization is less than the CFRM policy size, global resource serialization will issue message ISG322A. If you receive this message, check the coupling facility configuration. If either the policy size or the amount of storage available in the coupling facility is insufficient, global resource serialization issues message ISG338W.

The size of the lock structure can be tuned by checking the number of false contention occurrences in the resource management facility (RMF™) report. If the false contention rate is high (greater than one or two percent), use a larger lock structure (double the number of lock entries) to reduce the rate. You can increase the policy size for the structure and then rebuild the structure to reduce the amount of false contention. To rebuild a coupling facility structure, use the SETXCF STAR T, REBUILD command.

See Rebuilding the ISGLOCK structure on the use of the SETXCF command.