Mainframe programmers do not become aware that there is a checkpoint concept in DB2. Many guys assume that the CHECKPOINT concept is present only in IMS DB.
CHECKPOINT Concept
Let us see, which option in DB2 stores checkpoints. There is a “CHEKFREQ=” option. This option stores two parameters – how many checkpoints db2 has taken and time- duration.
- DB2 checkpoints are controlled using DSNZPARM and CHKFREQ.
- The CHKFREQ parameter is the number of minutes between checkpoints for a value of 1 to 60 or the number of log records written between DB2 checkpoints for a value of 200 to 16,000,000.
- The default value is 500,000. You may need different settings for this parameter depending on your workload. For example, you may want it higher during batch processing.
- CHKFREQ is a complex parameter to set because it requires a bounce of the DB2 subsystem to take effect. Use the SET LOG CHKTIME command to dynamically set the CHKFREQ parameter.
- In online CICS programs, during online processing, DB2 should checkpoint about every 5 to 10 minutes.
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