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How to Improve Performance 5-21
How Is Tuning Done?
How Is Tuning Done?
The first step in tuning is to determine the cause of frequent checkpoints. Are
the checkpoints occurring because the physical log is becoming full too
rapidly or as a result of some other event?
To answer this question, examine the value of the Numpage field in the
physical log portion of the DB-Monitor Status menu, Logs option, or in the
tbstat -l (lowercase -L) output. The physical log Numpage value is the number
of physical log pages used since the last checkpoint. If the value of Numpage
is close to 75 percent of the physical log size at the time that the checkpoint
begins, the checkpoint was probably initiated as a result of physical log
activity.
If this is the case, you can reduce the frequency of the checkpoint by
increasing the size of the physical log or increasing the specified value of
CKPTINTVL, the default checkpoint interval. If you wish to increase the
frequency of checkpoints, you can either reduce the size of the physical log
or reduce the specified value of CKPTINTVL, the default checkpoint interval.
(Refer to page 3-107 for more details about how to increase the size of the
physical log. Refer to page 3-109 for more details about how to change the
value of CKPTINTVL.)