Configuring and Tuning Databases on the Solaris™ Platform

Overview of the Buffer Cache

One of the main tools used by databases to reduce disk I/O is the database buffer cache. The database acquires a segment of shared memory and typically sets aside the largest proportion of it to hold database blocks (also referred to as database pages). When a transaction requires a block, it reads the block from disk and stores it in the buffer cache; subsequent transactions requesting the same block can then retrieve it from memory rather than from disk.

In practice, there is rarely enough memory in the buffer cache to accommodate every database block required by transactions, so blocks cannot be held in memory indefinitely. Databases use a least recently used algorithm to retain the most frequently accessed blocks ...