Oracle-L: RE: Oh Where Oh Where Is My Redo Coming From

From: John Kanagaraj <john.kanagaraj_at_hds.com>
Date: Fri, 21 Feb 2003 09:59:22 -0800
Message-ID: <F001.00554D0C.20030221095922@fatcity.com>

Ethan,

> monitoring is active and my stats are up to date I should be able to
> multiply the total number of updates, inserts and commits by
> the average row
> size and get a rough % of what objects are generating the most redo.

Note that the amount of redo does not depend on the average row size. It depends on the amount of _change_ (+ some overhead). This argument might skew the situation towards a table that has a large row size but that does not have that many updates...

> I am sure there are a number of other factors I need to
> consider, any ideas
> what they are?
> * Should I weight inserts, updates and deletes?
> * ??
>
> The goal is to identify the objects, then identify the jobs
> that work on
> those objects and see if I can reduce redo. I suspect a lot
> of this redo is
> being generated because of some poor design issues.

What you _do_ need to do is to use this SQL to detect the SIDs performing redo:

select sid, name, value
from v$statname n, v$sesstat v
where v.statistic# = n.statistic#
and name like 'redo size'
and value > 100000
order by value desc

You can then look at V$OPEN_CURSORS for those SIDs...

John Kanagaraj
Oracle Applications DBA
DBSoft Inc
(W): 408-970-7002

I don't know what the future holds for me, but I do know who holds my future!

The opinions and statements above are entirely my own and not those of my employer or clients ** -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: John Kanagaraj INET: john.kanagaraj_at_hds.com

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