Re: monitor cluster interconnect performance

From: <>
Date: Fri, 08 Aug 2008 21:11:40 +0200
Message-ID: <>

On Fri, 8 Aug 2008 11:22:52 -0700 (PDT), mike <> wrote:

>We have a 10g service that is load balanced between 2 RAC nodes. We
>noticed that query runs about 3x slower if the service is load
>balanced on both nodes vs running the service on a single node. We did
>verify that all traffic runs on the private network. On OEM, the GC
>block access latency was within 12 ms and the GC block transfer rate
>was within 30ms.
>Are these numbers considered high? What other queries or utilities can
>I use to monitor the performance of the interconnect?

Figures look pretty high.
Is your network configured correctly? (1G network, MTU set to 9k) Did you run racdiag.sql (available on Metalink)? Did you look at explain plans? Is there any impact of Cache Fusion? Do you have access to the Oracle Wait Interface Book? If not, buy it. It contains a section on RAC.
Likely Cache Fusion is killing you.
If your queries are unscalable, Cache Fusion will only make things worse, especially when your Interconnects have not been setup correctly.
In 9i RAC 1 multiblock request resulted in n global cache cr requests across the interlink. This has been fixed in 10gR2, but as you only post a marketing label instead of a version, I can't see whether you are still suffering from this 'feature'.


Sybrand Bakker
Senior Oracle DBA
Received on Fri Aug 08 2008 - 14:11:40 CDT

Original text of this message