RE: Job taking longer with more RAC nodes

Hameed,

In looking at the tkprof output, no rows were fetched in any of the
tests. This was after an even 1.2 *million* LIOs and all of this is just
EXEC (rather than FETCH)? An LIO is extremely/fully CPU intensive and
that is why your elapsed time is mostly taken up by cpu time. Was that a
valid SQL? Also, it seems that this is a custom code. 

In any case, I would assume that with RAC_ON, the kernel would go
through additional code to check cross-instance buffer status and hence
you suffer additional CPU usage for the same number of LIOs. (I am not a
RAC expert by any measure so take this with a big pinch of salt).

John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)
 
Co-Author: Oracle Database 10g Insider Solutions
http://www.amazon.com/exec/obidos/tg/detail/-/0672327910/
 
** The opinions and facts contained in this message are entirely mine
and do not reflect those of my employer or customers **


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Hameed, Amir
Sent: Thursday, March 09, 2006 1:54 PM
To: john d parker; oracle-l@xxxxxxxxxxxxx; racdba-bounce@xxxxxxxxxxxxx
Subject: RE: Job taking longer with more RAC nodes

This is an Oracle 11i application 11.5.9) and  the database version is
9.2.0.6 (64-bit). The thing that is surprising me is that there are no
RAC specific waits. It is the CPU usage that is going high. I am sure
there is an explanation to this and that is what I am trying to find
out.

-----Original Message-----
From: john d parker [mailto:orclwzrd@xxxxxxxxx]
Sent: Thursday, March 09, 2006 4:35 PM
To: Hameed, Amir; oracle-l@xxxxxxxxxxxxx; racdba-bounce@xxxxxxxxxxxxx
Subject: Re: Job taking longer with more RAC nodes

Do you have any degree of parallelism? or is parallel degree set to
default?

In general, A well behaved app will perform approx the same on RAC maybe
even marginally slower. A poorly behaved app will absolutely stink when
moved to RAC. RAC is not a performance enhancing solution.


John


--- "Hameed, Amir" <Amir.Hameed@xxxxxxxxx> wrote:

> Folks,
> I need some help in understanding why a job is taking longer when it 
> is run in multiple nodes under RAC versus a single node in RAC and 
> with RAC disabled.

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