# Prepared Plan Cache

+ `enabled` : Reduce the computational overhead caused by execution plans, so that statements of the same type use the same execution plan, and improve performance, at the cost of which execution plans may not be optimal when data or query conditions change.
+ `capacity` : Used to limit the size of the cache (number of cache entries) to avoid using too much memory. If the application uses a large number of different types of request and exceeds the capacity limit, the effect of plan cache will be compromised.


![left](./student-guide/diagram/06-prepared-plan-cache-01-01.png)
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Prepared Plan Cache
- enabled/capacity
  - Reduce computational overhead caused by execution plans after enabling statements of the same type to use the same execution plan, improving performance at the cost that execution plans may not be the best when data or query conditions change
  - Capacity is used to limit the size of the cache to avoid using too much memory. If the application uses a large number of different types of request and exceeds the capacity limit, the effect of plan cache will be compromised