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 Sql Server Strange Behaviour

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ilninno
Starting Member

2 Posts

Posted - 2012-08-28 : 15:42:15
Hello all,

We are having an strange problem:

We have two servers and two databases (Nearly the same data)

DB1 is running on server 1

DB2 is running on server 2

DB1 executes an sql script in 7 seconds

DB2 executes the same sql script in 600 seconds.

DB2 is copied to Server 1 in order to discard server performance issues, but the sql script run slowly too on this server.

Once is clear that server performance is not the problem, we think that is caused by small data variations:

The Scripts call to a view where it seems to be the problem:

Case 1: We replaced the view invocation for a replica table (same view data) and it works very fast.

Script calls table (equivalent to the view)

Case 2: As a result of this we think that the problem could be inside the view (it calls to smaller views), so we replace the smaller views call for the equivalent tables, but it works slowly.

Script calls View -> View calls tables (equivalent tables to the subviews)

Resume: The problem does not seems to be inside the view, because the Case 2 works slow. It seems that the problem is because we call the view, does it make sense? remember that this view is running fast on the DB1

Transaction logs has been trunked, Index has been rebuild, a DB shrink has been executed.

Thank you!!

tkizer
Almighty SQL Goddess

38200 Posts

Posted - 2012-08-28 : 15:54:27
You need to compare the execution plans. What is different between them? Scan vs. seek? Have you run update stats with fullscan on the tables involved on the problematic database?

Tara Kizer
Microsoft MVP for Windows Server System - SQL Server
http://weblogs.sqlteam.com/tarad/

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tkizer
Almighty SQL Goddess

38200 Posts

Posted - 2012-08-28 : 15:55:25
Have you freed the procedure cache on both systems to ensure the same baseline?

And just how much data variation is there?

Tara Kizer
Microsoft MVP for Windows Server System - SQL Server
http://weblogs.sqlteam.com/tarad/

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chadmat
The Chadinator

1974 Posts

Posted - 2012-08-28 : 17:17:34
Are indexes the same? Are the queries exactly the same (Parameters etc..). Free Data and Proc caches before each execution and compare the query plans as Tara suggested.

-Chad
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chadmat
The Chadinator

1974 Posts

Posted - 2012-08-28 : 17:18:12
Also, you can try updateing stats.

-Chad
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ilninno
Starting Member

2 Posts

Posted - 2012-08-28 : 17:59:22
It was the execution plan, we have cleaned the statistics and the procedure cache and now is working fine.

Thank you very much!!!
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tkizer
Almighty SQL Goddess

38200 Posts

Posted - 2012-08-28 : 18:19:45


Tara Kizer
Microsoft MVP for Windows Server System - SQL Server
http://weblogs.sqlteam.com/tarad/

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