AMPSUBZ parameter

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Number of active zIIP eligible subtasks


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


This parameter applies to z/OS only.

On a z/OS system, Model 204 zIIP support enables you to offload Model 204 work from regular processors to zIIP processors. AMPSUBZ specifies the number of active zIIP subtasks.

The value of AMPSUBZ must be less than or equal to the value of the NMPSUBZ parameter, which determines the number of zIIP subtasks attached during initialization.

Note: MP subtasks and zIIP subtasks may be used together. Therefore, AMPSUBS, NMPSUBS, AMPSUBZ and NMPSUBZ can all be greater than zero. However, to avoid unnecessary overhead:

  • Do not set AMPSUBS greater than the number of central processors actually available.
  • Do not set AMPSUBZ greater than the number of zIIP processors actually available.

If you set AMPSUBZ 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.