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If you have multiple instances of SQL Server running on the same windows server system,

a) Does buffer pool is shared amount multiple instances?

b) What is the effect of running DBCC DROPCLEANBUFFER OR DBCC FREEPROCCACHE? Would that only affect the SQL Server instance you ran the command on or all the instance(s) on the windows box would flush SQL server cache?

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migrated from Jan 11 '12 at 14:58

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Marthin Smith Thank you – SQL Learner Jan 11 '12 at 16:15
up vote 6 down vote accepted

The buffer pool in SQL Server isn't shared across intances.

DBCC DROPCLEANBUFFER removes all "clean" pages from the buffer pool, "clean" pages are pages which haven't been modified since being read into the buffer pool.

DBCC FREEPROCCACHE removes all cached execution plans from the plan cache.

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OK your answer make sense. Max Server Memory setting controls buffer pool memory allocated to that SQL instance. – SQL Learner Jan 11 '12 at 16:16
That correct Max Server Memory in SQL Server 2008 R2 and lower controls the Single Page Allocations, Multiple Page Allocations aren't controled by the Max Server Memory see for more details – MartinC Jan 11 '12 at 18:37

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