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SQL 2005 to 2008 SSRS CPU Spikes

Posted on 2011-02-10
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Last Modified: 2012-08-13
We recently migrated from SQL 2005 to SQL 2008.  Our SSRS reports worked fine in 2005.  Now that we are in 2008, when a report is run from a single user the CPU spikes to 100% and often the report ends up timing out.  We copied the database from our 2005 envirionment to our new 2008 environment.  We rebuilt the stats and indexes.

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Question by:cnewgard
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Expert Comment

by:Ryan McCauley
ID: 34871347
Is it just this one particular report that spikes the CPU, or is it a number of different reports?

If it's just this one report, it's possible that the database engine is making a different index choice in 2008 than it was in 2005. Can you post the query it's using? Any remote linked servers or other complexity in th query, or is it pretty standard stuff?

Also, do you still have a 2005 SSRS instance around somewhere that you could use the test this report? If you do, then you may be able to compare the execution plan to see what's different since your upgrade.
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Author Comment

by:cnewgard
ID: 34872572
All of our reports max the CPU.  I ended up installing an instance of SQL 2005 on the same box.  I moved my reports there and things are looking better.  I will check the execution plan of each and post my findings.
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Author Comment

by:cnewgard
ID: 34872601
Also, there are no complexities in the query.  No linked servers.  All datasets from the report pull from a single reporting database on the server.
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Accepted Solution

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Ryan McCauley earned 500 total points
ID: 34874663
That's really odd behavior, especially if there aren't any other circumstances in the queries that could cause the issue. Since it's happening across every report, it has to be a server-wide setting on your 2008 instance that's different than 2005.

Since you have a 2005 Reporting server handy, he's another questions - are the reports slow to execute on the 2008 SSRS instance, regardless of where the data is coming from (2005 or 2008), or are the reports slow to execute when they pull from a 2008 server? From what you're describing, it sounds like it's the first one, but I just wanted to clarify that.

Are you sure all the server settings are the same? x64/x86, degree of parallelism, installed on same disks (or at least some configuration), same memory allocation?
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Author Closing Comment

by:cnewgard
ID: 34988573
Expert was correct.  Execution plans were different.  The reports were also slow to run on 2005, just slower on 2008.  We decided to revamp our reporting and optimize it for 2008.  Thanks for all of your help!
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