The CFRM couple data set

Management of global resources in the star complex is performed through a coupling facility lock structure. The coupling facility is managed by the coupling facility resource management (CFRM) policy, which resides on the CFRM coupling facility data set.

The CFRM policy defines:

The lock structure
The amount of coupling facility storage to be used for the lock structure
The preference list of coupling facilities in which the structure resides, and
An unordered exclusion list of other structures that should not be allocated in the same coupling facility as the specified lock structure.

You must install and define at least one coupling facility to MVS™ before you can configure a star complex. However, IBM® suggests that you do not use the star method of serializing global resources if there is only one coupling facility available for use in your installation. In this case, failure of the coupling facility will result in termination of all the systems in the sysplex with an X'0A3' wait state.

Global resource serialization uses a lock structure, named ISGLOCK, to serialize global resources across the sysplex and record which systems have requesters for particular resources. You must specify ISGLOCK must in the CFRM policy by using ISGLOCK as the structure name on the NAME parameter.

Following is an example of the structure definition for the ISGLOCK structure. See Figure 1 to determine the size for ISGLOCK.

Figure 1. Specifying Global Resource Serialization Lock Structure in the CFRM Policy

 
   STRUCTURE
        NAME(ISGLOCK)
        SIZE(8448)
        PREFLIST(CFACIL01,CFACIL02)
        EXCLLIST(ABCSTR)

Note that the optional CFRM policy parameter, INITSIZE, is not specified in the ISGLOCK structure definition. It is not necessary to specify INITSIZE because global resource serialization does not support structure alter.

For information on managing coupling facility resources, see z/OS MVS Setting Up a Sysplex. For a discussion of GRS rebuild processing, see ISGLOCK rebuild processing.