| Changing execution plans [message #460572] |
Sat, 12 June 2010 10:55  |
NandKumar
Messages: 92
Registered: June 2007
Location: v$hyderabad
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Hi,
Ours is a four node RAC. Have observed that one particular select statement is running quite long occassionally on one node while its running very fast on some other node. To explain more clearly, today the query runs slow on instance 1. If we kill it and reexecute on say instance 2, its finishes quite fast. Tomorrow, the same query runs slow on node instance 3, but runs fast on instance 1. Have observed that the execution plan is changing from instance to instance. The initialization parameters are the same on all the instances.
Please suggest what can be the reason for this behaviour. Have checked the system stats. They are all same on all instances. Please provide some good performance tuning links and articles which might be helpful in this regard.
Regards
Nand
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| Re: Changing execution plans [message #460576 is a reply to message #460573] |
Sat, 12 June 2010 13:49  |
John Watson
Messages: 8931
Registered: January 2010
Location: Global Village
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Senior Member |
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It is difficult to comment on a statement that one has not seen. But if it uses bind variables, the bind variable peeking can cause the effect you describe
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