Re: Taking export from SECONDARY_INSTANCE from 02 node RAC

From: <sybrandb_at_hccnet.nl>
Date: Thu, 26 Feb 2009 19:17:03 +0100
Message-ID: <2rmdq4ptv2kkr8ufsu4p0thpddnpulsgbs_at_4ax.com>

On Thu, 26 Feb 2009 09:03:35 -0800 (PST), shweta.kaparwan_at_googlemail.com wrote:

>Hi All
>
>We are at :
>
>Oracle 9.2.0.6
>HP Ux : 11.23
>RAC : 02 Node
>( say node-A & node-B)
>
>
>
>Primary Instance is running in node-A & secondary instance running in
>node-B.
>
>All db connections goes to PRIMARY_INSTANCE , we control it via TNS.
> Hence at a given time PRIMARY_INSTANCE running in host-A is Active
>and SECONDARY_INSTANCE in host-B is UP but IDLE with respect to db
>connections. i.e. no connections goes to host-B.
>
>
>Now question:
>
>I want to start the export backup database ( size 50 GB) from host-B
>by connecting to SECONDARY_INSTANCE.
>
>i.e. my "exp" connection/session will be connecting to
>SECONDARY_INSTANCE in host-B.
>
>Whether this will cause " a ton of interconnect traffic all of a
>sudden as many of the blocks will have to be shipped for the first
>time to the other node".
>
>In simple words , how good it would be to export via
>SECONDARY_INSTANCE or are there any bad part of it in above scenario?
>
>
>Many Thanks
>
>Regards
>
>Shweta
>
>
>
>
>
>
>

It wouldn't matter as you are already greatly abusing RAC. If you don't use the second instance at all, you either don't need RAC, or you should configure RAC ClusterGuard I, which comes with RAC, and which is an active/passive configuration.

Also when a block isn't found on whatever instance, it will query the other instance, no matter whether that instance is loaded or not.

Importantly also a scattered read on 9iRAC for n blocks will result in n requests to the other node.

I observed a factor 5 speed increase during exp/imp when I just cluster_database to false.

So my advice is very simple:
Either upgrade to something supported (10g will request the n blocks at a time) or dump RAC completely. You don't need it, and you are wasting your money, simply due to your ignorance.

-- 


Sybrand Bakker
Senior Oracle DBA

Received on Thu Feb 26 2009 - 12:17:03 CST