Multisystem sysplex configuration without an existing global resource serialization complex

A sysplex requires a global resource serialization complex. The scope of the complex must encompass the scope of the sysplex. For information on creating a global resource serialization ring, see z/OS MVS Planning: Global Resource Serialization.

This topic assumes that you do not have an existing global resource serialization complex and want to IPL four systems into a 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 shared by all systems in a sysplex that includes more than one CPC.

As the systems are IPLed and join the sysplex, a global resource serialization complex is created for the systems in the sysplex. Thus, the sysplex and complex match as you IPL the systems.

Purpose: Use multisystem sysplex mode when you:
- Want XCF group services on the systems and signaling services between systems in the sysplex.
- Want to stop using the RESERVE macro to serialize global resources and start using the functions in a global resource serialization complex.
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 initializing system. COUPLExx must specify at least the sysplex name, the primary couple data set name (which must be shared by all systems), and sufficient outbound and inbound signaling paths to obtain connectivity with all other systems in the sysplex. Defaults can be taken for 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=00 (the default) specifies the GRSCNF00 parmlib member. GRSCNF00 contains global resource serialization parameters that can be used in the sysplex. You can specify GRSCNF=xx for a GRSCNFxx parmlib member if GRSCNF00 does not meet your installation's needs.
- GRSRNL=(xx,yy...) specifies the GRSRNLxx parmlib member(s) that contain the resource name lists (RNLs) that you require for the global resource serialization complex to meet your installation needs. (The GRSRNL00 parmlib member contains IBM® defaults.)
- CLOCK=xx specifies the CLOCKxx parmlib member that requests the Sysplex Timer to be used. MVS requires the Sysplex Timer to synchronize the coupling services.

As each of the MVS systems is IPLed, the sysplex and global resource serialization complex match, and consist of one, two, three, and then four systems. XCF coupling services and global resource serialization are available on the systems as they complete initialization.

Figure 1 shows the multisystem environment after the four systems are IPLed.

Figure 1. Multisystem Sysplex Configuration

Graphic Showing Multisystem Sysplex Configuration

After the four systems are IPLed, the multisystem sysplex configuration has:

XCF coupling services available on all systems, including signaling services between all of the systems in the sysplex.
The same primary sysplex couple data set shared by all systems in the sysplex (not shown).
MVS component exploiters (such as global resource serialization) that exploit the XCF coupling services.
Multisystem applications that can exploit the XCF coupling services in the sysplex.
The same Sysplex Timer on all systems, which synchronizes time stamps for all systems (not shown).