Re: Looking for pointers in troubleshooting -> RAC performance degradation (single instance is fine)
- From: Thomas Roach <troach@xxxxxxxxx>
- To: kaygopal@xxxxxxxxx
- Date: Fri, 25 Dec 2009 07:50:18 -0500
I agree with this approach. Start by identifying what segments (objects) the
contention is on. Also identify what SQL statements are causing those waits,
based on that, take steps to reduce the contention where it is occurring.
RAC or Non-RAC, you would see the contention issue. The fact that the blocks
now have to traverse the interconnect as multiple instance are requesting
the same block(s) just means that RAC is amplifying it.
I sent you a link in my first reply that should give you some insight on how
to identifying these things (objects with contention and sql statements).
On Fri, Dec 25, 2009 at 1:17 AM, K Gopalakrishnan <kaygopal@xxxxxxxxx>wrote:
> Pradeep,
>
> This might be a shot in the dark, but with a shotgun, you might hit some
> target :) In short this looks like an application issue, (or RAC amplifying
> the application noise).
>
> Treat gc buffer busy (and gc current busy) as you treat the buffer busy
> waits (or read by other session waits) and tune the storage for the segments
> accordingly. Techniques like MINIMIZE_RECORDS_PER_BLOCK at segment level or
> hash partitioning will yield great results.
>
> If you can post the relavant parts from the AWR we can offer a better
> solution :)(
>
> Happy Holidays and Happy New Year 2010.
>
> Best Regards,
> K Gopalakrishnan
>
> Oracle Database 10g Real Application Clusters Handbook
> http://www.amazon.com/gp/product/007146509X/
>
> Oracle Wait Interface: A Practical Guide to Performance Diagnostics &
> Tuning
> http://www.amazon.com/exec/obidos/tg/detail/-/007222729X/
>
>
> On Thu, Dec 24, 2009 at 7:28 AM, Pradeep Chetal <
> Pradeep.Chetal@xxxxxxxxxxxxxx> wrote:
>
>>
>>
>> Folks,
>>
>>
>>
>> We have an app that is running well in single instance but when put on a
>> 2-node or 3-node RAC, we see pretty much similar performance. However, if
>> the CPU time is 55-60% in single instance, it becomes 20% in 3-node RAC and
>> top-5 itmed events become..
>>
>>
>>
>> "gc buffer busy", "gc current block busy", "enq: TX- index contention
>>
>>
>>
>> Any help in what to look for will be greatly appreciated.
>>
>>
>>
>> Thanks,
>>
>>
>>
>> -- Pradeep
>>
>> *Pradeep Chetal*
>> Sr. Director - Infrastructure Architecture
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>
--
Thomas Roach
813-404-6066
troach@xxxxxxxxx
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