Hi,
we face some strange execution plan changes while upgrading the server hardware.
SQL Server Version: Microsoft SQL Server 2008 R2 (SP2) - 10.50.4000.0 (X64) Jun 28 2012 08:36:30 Copyright (c) Microsoft Corporation Enterprise Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)
It seems server memory has an effect on execution plan. Reconfigure the Server Memory down on the same box results in a different execution plan.
Can someone confirm that execution plans are memory dependent?
And how it effect the potential plan?
What I have observed
With max server memory at 200 GB (that was the value) we see an execution plan with estimated subtree costs 410700 and actual execution duration ~12 Minutes
With max server memory at 950 GB (that is the new value and no typing error) we see an execution plan with estimated subtree costs 403203 and actual execution duration ~120 Minutes (10 times the time)
(Same Box, Reconfigure - Execution on different day)
And yes, the IO System has some issues...
What changes - we get an additional table spool (eager) in the execution plan with the longer actual execution.
Any hint to official docuemntation...
Thank you
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