Greg Low, has published a whitepaper Plan Caching in SQL Server 2008, it's an update of the whitepaper "Batch compilation, Recompilation and Plan Caching Issues in SQL Server 2005" by Arun Marathe, targeted at SQL Server 2008.

Summary: This paper explains how SQL Server 2008 allocates memory for plan caching, how query batches are cached and suggests best practices on maximizing reuse of cached plans. It also explains scenarios in which batches are recompiled, and gives best practices for reducing or eliminating unnecessary recompilations and for minimizing plan cache pollution.

http://msdn.microsoft.com/en-us/library/ee343986.aspx

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