A buffer pool is a collection of buffers. The database buffer cache is divided into one or more buffer pools.
You can manually configure separate buffer pools that either keep data in the buffer cache or make the buffers available for new data immediately after using the data blocks. You can then assign specific schema objects to the appropriate buffer pool to control how blocks age out of the cache.
The possible buffer pools are as follows:
Default pool
This pool is the location where blocks are normally cached. Unless you manually configure separate pools, the default pool is the only buffer pool.
Keep pool
This pool is intended for blocks that were accessed frequently, but which aged out of the default pool because of lack of space. The goal of the keep buffer pool is to retain objects in memory, thus avoiding I/O operations.
Recycle pool
This pool is intended for blocks that are used infrequently. A recycle pool prevent objects from consuming unnecessary space in the cache.
You can create a tablespace with a block size that differs from the standard size. Each non default block size has its own pool. Oracle Database manages the blocks in these pools in the same way as in the default pool. The structure of the buffer cache when multiple pools are used. The cache contains default, keep, and recycle pools. The default block size is 8 KB. The cache contains separate pools for tablespaces that use the nonstandard block sizes of 2 KB, 4 KB, and 16 KB.
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