The size of a coupling facility structure is specified in the CFRM policy and also can be specified on the IXLCONN macro. Starting with SP 5.2, you also can specify an initial structure size with the INITSIZE parameter in the CFRM policy. The INITSIZE value is optional and is used only when an SP 5.2 and above system initially requests allocation of the structure in a coupling facility or subsequently requests a connection to a structure during user-managed rebuild processing.

With OS/390® Release 10 and higher, the CFRM policy can also specify a minimum structure size. MINSIZE specifies the minimum bound for structure allocation.

With z/OS V2R1 and higher, or z/OS V1R13 with PTFs for APAR OA40747, the CFRM policy can specify the SCMMAXSIZE keyword to indicate that a structure may use storage-class memory.