SCHDOPT1 parameter

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Flags that, in addition to the SCHDOPT parameter, allows one to tune scheduler behavior. SCHDOPT1 is a parameter where the following bits control a certain aspects of scheduler behavior:

X'01' Indicates that threads that are running on a zIIP-capable SRB and need to do journal I/O do not "bounce" to a non-zIIP subtask to do the journal or checkpoint I/O but simply perform it on the maintask. Since generally very little processing is involved in doing journal or checkpoint I/O, sending a thread to an MP task to do the I/O only increases latency and saves no maintask processing overhead.

This setting also prevents a thread running on a non-zIIP task and that has to wait for another thread doing journal or checkpoint I/O before doing the same from bouncing between maintask and subtask to do the I/O – when the X'01' bit is set, the I/O will be performed on the maintask, again reducing I/O latency. This bit has a much more significant effect if zIIP subtasks are in use. For more information about zIIP processing, refer to the SCHDOPT parameter and AMPSUBZ parameter descriptions.