ZQMAX parameter

From m204wiki
Jump to navigation Jump to search

Z queue max length (obsolete) (obs)


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


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.

ZQMAX limits the number of work units that may be placed for execution by the zIIP task.

The default and maximum value for ZQMAX is 65535.

  • If ZQMAX is set to a non-zero value: When a work unit is pushed onto the zIIP queue and the current zIIP queue length exceeds the value of ZQMAX, then that work unit is placed on the MP stack instead. Effectively, this limits the amount of work that is done on the zIIP and prevents zIIP overload.
  • If ZQMAX is set to zero: No users will be added to the zIIP queue. However, if the SCHDOPT X'80' bit is on and a zIIP task is active (AMPSUBZ greater than 0), then server swapping will occur on the zIIP task without the overhead of pushing zIIP work units onto the zIIP queue.

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

Usage notes

As of Model 204 version 7.6, ZQMAX is deprecated. If you have specified a value for ZQMAX, it is ignored in 7.6 and higher.