The Purpose of Cache

The main purpose of cache is to hold data that is likely to be used again in memory, therefore avoiding having to read the data in from disk again. If the cache is too:

• Small, the same database blocks are repeatedly read in from disk.

• Large, memory is wasted by holding blocks that are never re‑used.

The fundamental goal of tuning the caches is to minimize the number of database blocks that need to be re‑read from disk, for all databases on the machine.