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.