Snapshot Information Level Database Table Space Application |
API Structure(s) sqlm_dbase sqlm_tablespace sqlm_bp_info sqlm_appl |
Monitor Group Buffer Pool Buffer Pool Buffer Pool Buffer Pool |
Resettable |
Yes |
|
Event Information Level Database Table Space Connection |
API Structure(s) sqlm_db_event sqlm_tablespace_event sqlm_conn_event |
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API Element Name Element Type |
pool_index_writes counter |
Description: Indicates the number of times a buffer pool index page was physically written to disk.
Usage: Like a data page, a buffer pool index page is written to disk for the following reasons:
The system does not always write a page to make room for a new one. If the page has not been updated, it can simply be replaced. This replacement is not counted for this element.
The index page can be written by an asynchronous page-cleaner agent before the buffer pool space is required. These asynchronous index page writes are included in the value of this element in addition to synchronous index page writes (see "Buffer Pool Asynchronous Index Writes").
If a buffer pool index page is written to disk for a high percentage of the "Buffer Pool Index Physical Reads", you may be able to improve performance by increasing the number of buffer pool pages available for the database.
When calculating this percentage, disregard the number of physical reads required to initially fill the buffer pool. To determine the number of pages written:
In order to prevent the buffer pool from being deallocated between the runnings of your application, you should have another, idle application connected to the database.
If all applications are updating the database, increasing the size of the buffer pool may not have much impact on performance, since most of the pages contain updated data which must be written to disk.
See the Administration Guide for more information about the buffer pool configuration parameter (buffpage).
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