When IBM introduced basic sysplex, they required that at least a bare-bones global GRS be active on the systems that are part of a sysplex. In order for GRS and CA MIM to peacefully co-exist in a sysplex, IBM added the EXCLUDE value to the GRSRNL= parameter in IEASYSxx, and added the RNL=YES/NO parameter to the ENQ macro and parameter list.
The GRSRNL=EXCLUDE parameter setting caused GRS to demote all SYSTEMS scope ENQs to SYSTEM scope ENQs. This allowed GRS to be active in a system with CA MII also active, and prevented GRS from propagating ENQ requests that were already being propagated by CA MII.
However, IBM required serialization of resources that were sysplex-specific (ENQs with a scope of the local sysplex). Also, IBM required this resource serialization, particularly during sysplex initialization, when CA MII serialization might not be available.
To satisfy these requirements, IBM added the RNL=YES/NO parameter on the ENQ macro and parameter list. The default is RNL=YES. RNL=YES specified that an installation's RNL lists and their GRSRNL=EXCLUDE value, if specified, would be honored.
Specifying RNL=NO overrides both the installation's RNL specifications and their GRSRNL=EXCLUDE specification. Therefore, if an ENQ is issued with a scope of SYSTEMS and RNL=NO, GRS propagates this ENQ to all of the systems in the GRSPLEX (that is. all of the sysplex systems), even when GRSRNL=EXCLUDE is specified.
RNL=NO was intended to be used only on ENQ requests for resources that were sysplex-specific (that is, the scope of the local sysplex), or for resources that needed to be serialized during system and sysplex initialization.
To determine the GRSRNL value you are running with on a given system, issue the following z/OS command:
DISPLAY GRS,ALL
When an ENQ is issued on a sysplex system, and that ENQ has RNL=NO coded, CA MII bypasses those ENQ requests and passes them along to GRS. Recall that, in a sysplex, global GRS must be active, and all members of the sysplex must be members of the same GRSPLEX. This guarantees that the RNL=NO requests are propagated to all sysplex systems by GRS if the ENQ is scope SYSTEMS.
Unfortunately, the original IBM RNL=NO documentation did not express this intended function and was somewhat misleading, telling the user to "Use RNL=NO only when you are sure that you never want the scope value to change". IBM has since created APAR OW30729 to clarify the documentation on the RNL parameter.
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