Query Plan Caching

SQL Server 2014 has a pool of memory used to store both execution plans and data. The amount of memory allocated to execution plans or data changes dynamically, depending on the needs of the system. The portion of memory used to store execution plans is often referred to as the plan cache.

The first time a cacheable query is submitted to SQL Server, the query plan is compiled and put into the plan cache. Query plans are read-only re-entrant structures shared by multiple users. At most, there are two instances of a query plan at any time in the plan cache: a serial execution plan and parallel query execution plan. The same parallel execution plan is used for all parallel executions, regardless of the degree of parallelism. ...

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