Multisystem sysplex configuration on one processor under z/VM

This topic describes a multisystem sysplex on one processor under z/VM. The z/VM system must be ESA capable. Note that an XCF-local mode or single-system sysplex can be established under z/VM similar to those shown in XCF-local mode configuration and Single-system sysplex configuration. However, a sysplex running under z/VM cannot support a Sysplex Timer or a coupling facility.

Purpose: Use multisystem sysplex mode under z/VM for the reasons listed in Multisystem sysplex configuration without an existing global resource serialization complex and Multisystem sysplex configuration with an global resource serialization complex. In a multisystem sysplex on one processor under z/VM, a simulated Sysplex Timer must be used.
Each of the MVS™ systems in the sysplex must be under a single host z/VM on one processor.
Considerations: A multisystem sysplex on one processor under z/VM should have APAR VM58844 installed. This APAR supports the CP SET command that you must issue for any DASD that contains any type of XCF couple data set to avoid integrity exposures.
- SET WRKALLEG (for VM/ESA Release 1.2.2 and above)
- SET SHARED (for VM/ESA releases prior to Release 1.2.2)
XCF will remove data sets that appear to have suffered an integrity exposure. If XCF removes both the primary and alternate data set for any type of XCF couple data, the function using that data set might cause one or more systems in the sysplex to enter a disabled wait state or might lose some of its function due to its inability to access its sysplex shared data.
Required System Parameters: Use the following system parameters to initialize each MVS system:
- CLOCK=xx specifies the CLOCKxx parmlib member that requests the same simulated Sysplex Timer (SIMETRID xx) on all systems.
- Other system parameters for a multisystem sysplex as described in the preceding topics.

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