Buffer pool is part of main memory space. This space is allotted by the database manager. It cache table and index data from the disk.
In the context of IBM Db2, a buffer pool is a memory area that is used to cache data pages and index pages from database tables. The purpose of a buffer pool is to reduce the physical I/O operations by keeping frequently accessed data in memory, which can significantly improve query performance.
When a program or query needs to access data from a table, Db2 checks if the required data pages are already in the buffer pool. If the pages are found in the buffer pool, it is a cache hit, and the data can be retrieved directly from memory, avoiding the need to read from disk. If the pages are not in the buffer pool, it is a cache miss, and Db2 has to read the data from disk into the buffer pool before providing it to the program or query.
Buffer pools are defined and managed by the database administrator, and the size of the buffer pool can be adjusted based on the workload and available system memory. Multiple buffer pools can be defined in a Db2 database, each associated with specific table spaces or types of data to optimize performance.
In summary, a buffer pool in Db2 is a critical component for improving data access speed by caching frequently used data in memory.