There are several SRM/WLM options that allow you to control how work is assigned between zIIPs and standard CPs. zIIP-eligible work may also execute on standard CPs in order to achieve workload goals.
Parmlib member IEAOPTxx contains the IIPHONORPRIORITY statement which controls the workflow to zIIPs. If you specifiy IIPHONORPRIORITY=YES this indicates that standard CPs may execute zIIP-eligible and non-zIIP-eligible work in priority order, if zIIP processors are unable to execute all zIIP-eligible work. This is the default.
Specifying IIPHONORPRIORITY=NO means
that standard processors will not process zIIP processor eligible
work unless it is necessary to resolve contention for resources
with non-zIIP processor eligible work.
Note that the IFACROSSOVER=YES option in IEAOPTxx SYS1.PARMLIB is not applicable for either zIIPs or zAAPs. If specified, it is ignored.
See z/OS MVS Initialization and Tuning Reference for more information on the parmlib member IEAOPTxx.