RE: Looking for pointers in troubleshooting -> RAC performance degradation (single instance is fine)

Thomas,  

There are lot of updates (not inserts) but on some of the tables that are populated by sequences and others without sequences.  

I will go through this and see if this helps.  

Thanks,  

• Pradeep

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From: Thomas Roach [mailto:troach_at_gmail.com] Sent: Thursday, December 24, 2009 9:08 AM To: Pradeep Chetal
Cc: oracle-l_at_freelists.org
Subject: Re: Looking for pointers in troubleshooting -> RAC performance degradation (single instance is fine)  

Sorry to early.. meant that it might "NOT" be the right solution for you :)

On Thu, Dec 24, 2009 at 9:07 AM, Thomas Roach <troach_at_gmail.com> wrote:

Hi,

Are you doing a lot of inserts/updates to tables that have indexes that are populated by sequences? You should find the objects the contention is on. To assist with this, take a look at this page. http://www.ardentperf.com/2007/09/12/gc-buffer-busy-waits-in-rac-finding
-hot-blocks/

Basically what "could" be happening (what happened with me) was that I had a bunch of sessions across nodes all fighting to put entries into the same index blocks. Even on one node, this would be a contention issue. What I did to fix my issue was identify the indexes with the contention and made them reverse key indexes. With reverse key indexes you lose the ability to perform certain operations like an index range scan. So if you do queries where something is between this value and that value etc, it might be the right solution for you.

Good Luck.

On Thu, Dec 24, 2009 at 8:28 AM, Pradeep Chetal <Pradeep.Chetal_at_mformation.com> 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

Mformation Technologies Inc.
Switchboard: +1 732 692 6200  

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Thomas Roach
813-404-6066
troach_at_gmail.com  

Visit WWW.MFORMATION.COM and see how the MFORMATION SERVICE MANAGER can help you to transform your business

This message and the information contained herein is proprietary and confidential and subject to the Mformation Confidentiality policy statement, you may request a copy by emailing info_at_mformation.com

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http://www.freelists.org/webpage/oracle-l Received on Thu Dec 24 2009 - 08:29:32 CST