Re: Performance problems after moving to new hardware

send a sql Monitor report from this and you will get answers. Normally on plan changes a bad cardinality estimate is the root cause. To find out compare estimated rows versus atctual rows in sql monitor. That technique is called cardinality feedback. If the cardinality estimate is wrong I/O calibration won't solve your root cause. It will just shift cost calculation a bit.
If I/O calibration cures your issue you have a good chance the cure won't last.

Thanks

Lothar

On 04.03.2015 14:25, Sandra Becker wrote:
> OS: Solaris Sparc 10 (64-bit)
> Oracle: EE 11.2.0.2
>
> The OS and Oracle versions are identical on both the old and new
> servers. Storage attached to the new server is a new EMC disk array.
> Sorry I don't have any more details on the storage and the only
> additional information I have on the server is that it is a T5.
>
> We created a standby on the new hardware and did a switchover last
> Friday night. On Saturday I completed gathering stats on the
> application schema tables as requested by the product manager. As
> usual, very little activity on this database over the weekend.
> Yesterday morning we were contacted by internal users that performance
> was much worse than on the old hardware for a specific query on a
> really ugly view. A look at the execution plan shows multiple full
> table scans on some partitioned tables, some very large. There are
> about 15 tables joined to create the view, some more than once. They
> claim the view is no longer doing partition pruning, as it did before
> the switchover. I can't prove that it was/wasn't exhibiting this
> behavior before the switchover. They are insisting we run I/O
> calibration. I'm not familiar with it so I went to the docs. This
> database shares storage with quite a few production databases so I
> want to be very careful how I go about this.
>
> Questions:
>
> 1. What will running the I/O calibration do? Does it only provide
> information on the I/O subsystem, or does it change the way the
> optimizer behaves? The development team insists it will improve
> performance.
> 2. I've looked at AWR reports before/after the switchover and see
> that the query in question was doing a similar amount of I/O in both
> reports. Is there any way for me to get more detail on the before
> execution plan?
> 3. One of the large partitioned tables has no indexes. Would creating
> an index be of any benefit? I understand that it's possible to
> negatively affect other queries, so it should be considered with
> caution. Development insists that indexing would be a waste of time
> and definitely cause problems, although they have never tested it.
> 4. I want to trace the query, but it runs in parallel and produces
> more trace data that I have available disk to handle. Is there
> anything I can do on that front to get a trace I can feed into my
> Method-R tool and supply to oracle support?
>
> As I reviewed how the view, I recall them having issues with it before
> and me suggesting it should be optimized. I was told no and here we
> are again. The obvious concern is that the results would be different
> and changes require a lot of testing they don't have time to do. Any
> other recommendations would be appreciated.
>
> --
> Sandy
> GHX

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