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DB2 - What is buffer pool? Where we use it ?

asked mar August 20, 2014 12:16 PM  

What is buffer pool? Where we use it ?


1 Answers

answered By Mswami   0  
Buffer pools:

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.

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.

You can specify default buffer pools for user data and for indexes. A special type of buffer pool that is used only in Parallel Sysplex data sharing is the group buffer pool, which resides in the coupling facility. Group buffer pools reside in a special PR/SM LPAR logical partition called a coupling facility, which enables several DB2 subsystems to share information and control the coherency of data.

Buffer pools reside in the DBM1 address space. The maximum size of a buffer pool is 1 TB.

Buffer pools are a key element of DB2 performance, and help you to avoid delays when retrieving data.

DB2 can retrieve a page from a buffer pool faster than it can from disk. When data is already in a buffer, an application program avoids the delay of waiting for DB2 to retrieve the data from disk.

You can specify that DB2 uses up to 50 buffer pools that contain 4 KB pages. You can also specify up to 10 buffer pools each that contain 8 KB, 16 KB, and 32 KB pages.
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