SCHDOPT1 parameter

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

Setting

Meaning

X'01'

Journal and checkpoint I/O cannot be performed on a zIIP subtask; that I/O operation must start on an MP subtask or on the maintask. When this parameter is set to X’01’, a user running on a zIIP subtask who needs to write to the CCAJRNL/JLOG or CHKPOINT data set, will be switched to the maintask, not an MP subtask, and the I/O operation will start on the maintask. Waits for an MP subtask to become available on a busy system can be significantly longer than waits for the maintask to become available. There is also more overhead to switch to an MP subtask than to the maintask. Consequently, this feature reduces wait times to start an I/O to the CCAJRNL/JLOG and CHKPOINT data sets when a unit of work is running on a zIIP subtask. For more information about zIIP processing, refer to the descriptions for theAMPSUBZ parameter, MPDELAYZ parameter, NMPSUBZ parameter, SCHDOFLS parameter and SCHDOFLZ parameter.