Re: Performance problems after moving to new hardware
Date: Wed, 4 Mar 2015 08:24:51 -0600
Message-ID: <CAJvnOJY6DZvOKRVdtVsiU-Ft8zs5bOBVOBNdvhz6Av5DpVTzvQ_at_mail.gmail.com>
This does look like a tough one. However, calibrate_io shouldnt break anything. If you have the tuning pack, you might want to run the sql tuning advisor and see if it makes any suggestions. Also, you might want to look at the plan and verify whether or not it is running partition pruning. Did you check your init.ora settings and see if their are any major differences that could account for the problem?
On Wed, Mar 4, 2015 at 7:25 AM, Sandra Becker <sbecker6925_at_gmail.com> 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
>
-- Andrew W. Kerber 'If at first you dont succeed, dont take up skydiving.' -- http://www.freelists.org/webpage/oracle-lReceived on Wed Mar 04 2015 - 15:24:51 CET