Delay Type

Reason

Demand paging

One or more of the following situations might be present in the program or in one of the subroutines it calls:

• a program is link-edited inefficiently
• data arrays are used incorrectly
• too many data buffers are specified

VIO paging

VIO data sets are simulated files that can significantly reduce I/O delays.

They are essentially paging files that are managed by z/OS. The only drawback is that, if the application requests a record that is not in the VIO panel, a page fault will occur that will not be processed concurrently with the application program and the application will experience delay.

Swapping

This delay is caused when

• the program or one of its subroutines is requesting system resources that are unavailable
• the site’s tuning parameters are improperly set