Examining the effects of checkpoints

Checkpoint processing can be initiated by the control program at a specified frequency determined by the number of records placed on the system log. Other checkpoints can be caused by operator commands.

The checkpoint line of the Region Summary report at the end of the region 0 summary shows the following:

• The number of system checkpoint taken during the monitor interval
• The elapsed times
• The not-wait times

The wait time experienced during checkpoints is reported at the end of the first region summary on the Region Wait report. You can detect delays for each combination of DD name and module code. Typical entries here are for the message queue data sets and the restart data set. If an wait for storage is the cause, the entry under the FUNCTION column is STG.=, followed by the identification of the pool.