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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. At least one coupling facility must be installed and defined to MVS before you can configure a star complex. However, IBM recommends 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 all of the systems in the sysplex being terminated with a X'0A3' wait state.

The IGSLOCK structure size is dependent upon the following factors:

• The size and type of systems in the sysplex

• The type of workload being performed.

Global resource serialization requires that the lock structure contains at least 32767 (32k) locks. Typically, a small sysplex, made up of smaller processors, running a transaction processing workload will use a smaller structure size than a larger sysplex, composed of large processors, running a batch/TSO workload combination.

Peak Number of Global Resources

The number of peak global resources equals the number of unique globally managed resources (SYSTEMS ENQs and converted RESERVEs) outstanding, measured at a peak load time.

 

The utility program ISGCGRS, available in SYS1.LINKLIB, can be used to obtain the number of outstanding global requests. The number of outstanding requests is shown in the third column of the report. To execute the utility, use the sample JCL found in SYS1.SAMPLIB member ISGCGRS.

//IANWAIT JOB (999,POK),CLASS=A,MSGCLASS=X,TIME=440
//STEP001 EXEC PGM=ISGSCGRS

12:11:49:06 IANWAIT 00000090 IEF403I IANWAIT - STARTED - TIME=12:11:49
12:11:49:14 IANWAIT 00000090 +Number of global resources outstanding
12:11:59:20 IANWAIT 00000090 +Number of global resources outstanding
12:12:09:26 IANWAIT 00000090 +Number of global resources outstanding
12:12:19:32 IANWAIT 00000090 +Number of global resources outstanding
12:12:29:37 IANWAIT 00000090 +Number of global resources outstanding

Max Number of Connectors

The maximum number of connectors per structure specified when the primary CFRM couple data set was formatted (ITEM NAME(CONNECT) NUMBER(xx)). CFSizer will use the smaller of this number or the release-specific maximum number of systems in a sysplex. If you bring into use a new primary CFRM couple data set formatted for a greater number of connectors per structure, you must repeat this calculation, since the new value will be applied if you rebuild the structure or re-IPL the sysplex.