The following topics describe hardware requirements for XRC:
- ESA/390 hardware.
- Your ES/9000 environment
must be compatible. The XRC primary system builds on the existing
sysplex concept to ensure sequence consistency. You must have a sysplex
timer if multiple processing units update XRC primary volumes. The
system clock is sufficient in a single processor or virtual server
environment.
- The system data mover must have access to the control, state,
and journal data sets, and to the primary and secondary copy volumes.
If you are going to configure a coupled environment, all SDM hosts
must have access to a shared volume that contains the master data
set.
- All host primary systems must have a common time reference. This
is necessary so that XRC can provide data consistency for all volume
updates across all attached host systems. Host system MVS/DFP software
performs timestamping of all application I/O write operations to active
XRC volumes. Therefore, all channel programs issued to XRC-managed
volumes are timestamped with a common time reference.
Examples: The following are examples
of common time references:
- The system time-of-day clock provides the common time reference
for environments with either a single processor, or with multiple
virtual servers defined.
- In an environment with multiple processing units, the sysplex
timer, or equivalent, provides the common time reference for application
programs. XRC and application programs both require a common time
reference.
- Although the primary application systems require a common timer
reference so XRC can properly order dependent application I/Os, the
XRC system itself does not need to be attached a sysplex timer.
- A compatible secondary volume must be available for each primary
volume you wish to copy. The secondary volume must have the identical
track capacity and number of tracks per cylinder and either the same
or larger volume capacity.