HiperDispatch provides a performance improvement by optimizing
the use of system cache. The performance gain HiperDispatch provides
typically increases with a newer hardware generation and can
improve with newer releases of z/OS®.
Before enabling HiperDispatch for the first time, review the
"Planning Considerations for HiperDispatch Mode" White Paper
located on IBM Techdocs at http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP101229.
When
a machine of a newer hardware generation is installed, for any z/OS partition(s) that are running
with HiperDispatch disabled, the system programmer should reevaluate
whether those z/OS partition(s)
should be migrated to run with HiperDispatch enabled in the new
environment.
When a new z/OS release
contains a noteworthy performance improvement for HiperDispatch=YES,
the date of the Health Check will be updated. The date is updated
to alert the system programmer that partitions running with HiperDispatch
disabled should be reevaluated to see if it is appropriate to
migrate those partitions to HiperDispatch enabled.
On any z/OS release running on IBM System z10 hardware, HiperDispatch disabled
is the default. On IBM System z10 systems, customers
are encouraged to try running with HiperDispatch enabled.
Beginning
with z/OS V1R13 on zEnterprise® 196 hardware,
HiperDispatch enabled is the default. With zEnterprise 196 hardware, z/OS partitions with share greater
than two physical processors will typically experience improved
processor efficiency with HiperDispatch enabled. z/OS partitions with share less than 2 physical
processors typically do not receive a detectable performance improvement
with HiperDispatch enabled, but IBM recommends
running those partitions with HiperDispatch enabled when the performance
improvement is greater than or equal to HiperDispatch disabled.
Initially all z/OS partitions
on non-IBM System z10 machines
that run HiperDispatch disabled will result in this Health Check
raising an exception. The system programmer can supply the machine
type to this Health Check to indicate that a partition is intentionally
running with HiperDispatch disabled on a particular machine type.
IBM suggests that all
partitions that experience improved or equivalent processor efficiency
with HiperDispatch enabled continue running with HiperDispatch
enabled.