Query Optimization is resource-intensive process that could introduce significant CPU load on busy servers. SQL Server tries to minimize such load by caching plans in a special part of process memory called plan cache.
This chapter talks about plan caching in detail, and it consists of two parts: the first part provides a high-level overview of plan caching, and it discusses several issues associated with it. The second part dives deeper into plan cache internals, and it discusses the various data management views that you can use for plan cache monitoring.
Plan Caching Overview
SQL Server prevents unnecessary recompilations ...