NMPSUBZ parameter

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Number of zIIP eligible subtasks


Default value
Parameter type
Where set
On User 0's parameter line
Related products
Model 204 V7.4


Model 204 can run a portion of workload on IBM System z Integrated Information Processor (zIIP) engines. The only unit of work that z/OS schedules to run on a zIIP is the enclave Service Request Block (SRB). An enclave is a collection of resources, such as address spaces, TCBs, and SRBs, that are controlled by Workload Manager (WLM) as an entity. Therefore, an enclave SRB is a part of an enclave.

Model 204 creates an enclave SRB with the same dispatching priorities as the maintask. Model 204 uses an enclave SRB, in this case zIIP, in the same way as an MP subtask. The term zIIP subtask is the equivalent of enclave SRB.

The NMPSUBZ parameter initiates a zIIP infrastructure. If NMPSUBZ is not zero, a zIIP-related infrastructure is created, and NMPSUBZ specifies the number of zIIP subtasks attached during initialization (enclave SRBs).

As many as NMPSUBZ defined special subtasks (named zIIP tasks) are attached. The zIIP tasks are real tasks as opposed to zIIP subtasks, which are enclave SRBs. The zIIP tasks are used only for exception handling and enclave SRB creation and deletion. Each active zIIP task creates an enclave SRB at initialization.

Note: MP subtasks and zIIP subtasks may be used together. Therefore, AMPSUBS, NMPSUBS, AMPSUBZ, and NMPSUBZ may all be greater than zero.

If you set NMPSUBZ greater than 0, the X'02' bit of the XMEMOPT parameter (the default), must also be set.

For more information about zIIP processing, refer to Offloading Model 204 work to zIIP processors.