IBM 000-8697 Uživatelský manuál stáhnout pdf (Strana 461)

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How to Improve Performance 5-21

How Is Tuning Done?

Theﬁrststepintuningisto determine the cause of frequentcheckpoints.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.ThephysicallogNumpage 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 speciﬁedvalue 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.)

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