Paging problems

The page-in rate is of primary concern, because page-in activity occurs synchronously (that is, a z/OS task stops until the page fault is resolved). Page-out activity overlaps with IBM Z Workload Scheduler processing, so it does not appreciably affect throughput.

A page-in from expanded storage incurs only a small processor usage cost but a page-in from DASD incurs a time cost for the physical I/O and a more significant increase in processor usage.

Thus, extra DASD page-in activity slows down the rate at which transactions are processed by the Z controller. If you suspect that a performance problem is related to excessive paging, you can use RMF™ to obtain the paging rates.