Tuning database buffer pools
Buffer pools require monitoring and tuning. Buffer pool sizes are critical to the performance characteristics of an application or group of applications that access data in those buffer pools.
About this task
Buffer pools are areas of virtual storage that temporarily store pages of table spaces or indexes.
When an application program accesses a row of a table, Db2 places the page that contains that row in a buffer. Access to data in this temporary storage is faster than accessing data on a disk. If the required data is already in a buffer, the application program does not need to wait for it to be retrieved from disk, so the time and cost of retrieving the page is reduced.
If the row is changed, the data in the buffer must be written back to disk eventually. But that write operation might be delayed until Db2 takes a checkpoint, or until one of the related write thresholds is reached. (In a data sharing environment, however, the writing mechanism is somewhat different. .) The data remains in the buffer until Db2 decides to use the space for another page. Until that time, the data can be read or changed without a disk I/O operation.
Buffer pools reside in the database services address space (ssnmDBM1).
The
maximum size of a buffer pool is 16 TB.
what ifanalysis of your buffer pools.
Procedure
To change the size and other characteristics of a buffer pool, or enable Db2 automatic buffer pool size management: