BufferPoolHitRatio (DB2UDB_BUFFERPOOL)
Indicates the percentage of the data and index reads that did not require access to the physical disk because the data was already loaded in the cached memory buffer pool.
The BUFFERPOOL DB2 Monitor Switch must be set ON to make this parameter active and collect data.
This parameter uses the delta calculations.
Recommendation
If the buffer pool hit ratio is consistently low, perform one of the following actions:
Increase the size of the buffer pool | Increase the size of the buffer pool in small increments and stop increasing it when the hit ratio stops improving. Do not make the buffer pool too large to be held in the physical memory. Otherwise, any performance improvements that you gain from the increased size can be offset by paging operations. |
Create additional buffer pools | For very large databases, a low overall hit ratio might be unavoidable. By creating separate buffer pools for specific types of data could help the situation. You can then focus your tuning efforts on indexes and frequently accessed tables. |
Parameter value calculation
Note: During first collection cycle, the BufferPoolHitRatio parameter would not populate a value since there is no value for the previous buffer pool physical and logical reads. From next collection cycle, parameter will compute and populate the value. Also, the BufferPoolHitRatio parameter will go into an offline state during first collection cycle, however, parameter will return to online state from the next collection cycle.
Default parameter attributes
Attribute | Default value |
|---|---|
Application class | DB2UDB_BUFFERPOOL |
Command type | not applicable |
Platform | All |
Active at installation | yes |
Parameter type | Consumer |
Scheduling (poll time) | not applicable |
Icon style | Graph |
Alarm 1 range | not applicable |
Alarm 2 range | not applicable |
Border range | not applicable |
Unit | Percentage |
Annotated? | No |
Value set by | CollBufferpool |