Central storage is a critical resource exploited by DFSORT to reduce I/O and improve performance. DFSORT exploits available storage to create memory objects, Hiperspaces and data spaces. Overcommitment of these resources can lead to excessive paging that negatively impacts the performance of DFSORT and other workloads running on the same system.

To be meaningful, paging and swapping activity measurements are usually associated with particular workloads, or groups of applications that are run simultaneously on a given processor. As such, system paging activity is more a measure of the performance and throughput of the entire system than of the performance of individual applications being run on the system.

Paging activity is often measured by the page-in, page-out, and page-reclaim rates of different address space types, such as Hiperspace, VIO, or non-VIO address spaces. For swapping activity, there is also the additional distinction between logical and physical swaps.

Central storage resource statistics and system paging and swapping activity data are usually gathered by the Resource Measurement Facility (RMF) or a similar system tool. See z/OS RMF Report Analysis for more information on RMF.