Shulou(Shulou.com)06/01 Report--

Definition:

A shared pool (shared pool) is an area of memory located in SGA and is mainly used to cache the execution plan of SQL. It is called sharing because this block of memory area can be shared by multiple sessions with the same execution plan. That is, if a session executes SQL, an execution plan of the statement will be generated in shared pool, and if the second session uses the same or similar statement, the execution plan can be reused to share the execution plan.

Features: 1 shared pool is an important memory area in SGA, because it stores the SQL execution plan and results, as well as some other types of files, such as control files.

2 the shared pool is expensive, and the system resources consumed by maintaining a shared pool are huge. If the shared pool is too large, it will consume more system resources to maintain it. If it is too small, it will not be enough, that is, the execution plan that should be shared is not shared because the shared pool is too small, but repeated hard parsing (hard parse) will also lead to waste of CPU resources.

3 the shared pool is similar to the cache of the system and is maintained by the policy of LRU.

4 to avoid memory fragmentation, there are a large number of Mini Program blocks.

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