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Snapshot Level Database |
Logical Data Grouping dbase |
Monitor Switch Buffer Pool |
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Resettable |
Yes |
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Event Type Database |
Logical Data Grouping db_event |
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Element Name Element Type |
pool_drty_pg_steal_clns counter |
Description: The number of times a page cleaner was invoked because a synchronous write was needed during the victim buffer replacement for the database.
Usage: Using the following formula, you may calculate what percentage of all cleaner invocations are represented by this element:
buffer pool victim page cleaners triggered
/ ( buffer pool victim page cleaners triggered
+ buffer pool threshold cleaners triggered
+ buffer pool log space cleaners triggered)
If this ratio is low, it may indicate that you have defined too many page cleaners. If your chngpgs_thresh is set too low, you may be writing out pages that you will dirty later. Aggressive cleaning defeats one purpose of the buffer pool, that is to defer writing to the last possible moment.
If this ratio is high, it may indicate that you have too few page cleaners defined. Too few page cleaners will increase recovery time after failures (see the Administration Guide).
| Note: | Although dirty pages are written out to disk, the pages are not removed from the buffer pool right away, unless the space is needed to read in new pages. |