Multisystem sysplex configuration with an global resource serialization complex

This topic assumes that you have an existing global resource serialization complex of four systems and want to initialize them into a sysplex that matches the complex.

Until all systems are IPLed and join the sysplex, a mixed complex exists; that is, one or more of the systems in the global resource serialization complex are not part of the sysplex.

In multisystem sysplex mode, you need:

A formatted primary sysplex couple data set shared by all systems in the sysplex.
Signaling connectivity between all systems in the sysplex
The same Sysplex Timer for all systems in a sysplex that includes more than one CPC.

Purpose: Use multisystem sysplex mode with an existing global resource serialization complex when you want XCF services on the initializing systems and signaling services between the systems in the sysplex.
Required System Parameters: Use the following system parameters to initialize each MVS™ system:
- COUPLE=xx specifies the COUPLExx parmlib member that describes the sysplex environment for the system. COUPLExx must specify at least the sysplex name, the primary couple data set name (which must be shared by all systems in the sysplex), and sufficient outbound and inbound paths to obtain full signaling connectivity with all other systems in the sysplex. Defaults can be taken for the other parameters.
- PLEXCFG=MULTISYSTEM indicates that the system is to initialize as part of a multisystem sysplex.
- GRS=TRYJOIN specifies that the system is to join an existing global resource serialization complex or start one.
- GRSCNF=xx specifies the GRSCNFxx parmlib member for the existing global resource serialization complex. This includes the definitions of the necessary CTC links for the complex as systems are migrated into the sysplex. When the sysplex matches the complex, global resource serialization uses signaling services and no longer needs its own CTC links between systems.
- GRSRNL=(xx,yy...) specifies the GRSRNLxx parmlib member(s) that contain the resource name lists (RNLs) that you require for the complex to meet your installation needs.
- CLOCK=xx specifies the CLOCKxx parmlib member that requests the Sysplex Timer to be used. MVS requires the Sysplex Timer to synchronize coupling services in the sysplex.

The following topics describe the multisystem environment as each of the four systems are initialized in order (SYSA, SYSB, SYSC, and then SYSD).