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Home -> Community -> Mailing Lists -> Oracle-L -> RE: SHOULD WE ANALYZE 9.2 SYS tables?
Hi Michael,
thanks for disagreeing with me ;-)
is this an apps environment, by any chance?
I heard stories about specific problems with DD stats in such environments. again, it is not recommended in Oracle9i, as I said -- but it also insn't forbidden.
By the way, I think Metalink notes are very useful, most of the time -- but they do not (and cannot) reflect the official Oracle guidelines about how the Oracle software should be used; there are many customers who have no access to Metalink in the first place. I don't see a reason why you would need internal Oracle guidance in these matters for Oracle9i.
Moreover, this evolved into a guideline that you actually *should* collect
stats on the DD
for Oracle 10g, even including stats for the fixed X$ tables...
Kind regards,
Lex.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Michael Fontana
Sent: Thursday, July 29, 2004 20:19
To: oracle-l_at_freelists.org
Subject: RE: SHOULD WE ANALYZE 9.2 SYS tables?
Lex, I disagree with your disagreement, but let me qualify.
Oracle "discourages" collecting statistics gathering "in most cases" per note 35272.1, as mentioned in my previous posting. The qualify this to say that in certain larger implementations, statistics can be selectively applied to certain dictionary objects, but even then, only with internal Oracle guidance.
Therefore, let's conclude, that for the general populace, collecting statistics for the ENTIRE schema is not recommended. Oracle also mentions, in this article, that they have no plans to change this.
We have both Oracle8i and oracle9i implementations in my shop. I assure you we will immediately notice severe performance degradation if stats are applied to SYS. It's already happened...for 95% of Oracle installations, it's my opinion that they'd be better off staying away from it.
Michael Fontana
Sr. DBA
NTT/Verio
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Lex de Haan
Sent: Thursday, July 29, 2004 2:08 PM
To: oracle-l_at_freelists.org
Subject: RE: SHOULD WE ANALYZE 9.2 SYS tables?
I must disagree here.
it is true that Oracle never actively encouraged customers to gather
statistics for the SYS schema in Oracle9i, but it certainly cannot ruin
your performance. Oracle also doesn't explicitly forbid you to gather DD
statistics. you have to go back further in time (Oracle8i) to get into
trouble with data dictionary statistics. I discussed this with the
optimizer development team (when I was still inside Oracle) and they
told me that there are no reasons at all *not* to gather statistics on
the SYS schema. In other words, feel free.
as you probably know, various Oracle9i DD views actually have hints in their definitions, kicking in CBO anyway ...
Kind regards,
Lex.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Juan Carlos Reyes
Pacheco
Sent: Thursday, July 29, 2004 19:42
To: oracle-l_at_freelists.org
Subject: Re: SHOULD WE ANALYZE 9.2 SYS tables?
Hi Larry
SYS schema don't need be analyzed, using tom kyte's word "it's magical"
and must not be analyzed if you got statistics in sys, you can ruin it's
performance. sys schema don't have to be touched, this means don't
create user tables in sys, etc.
Juan Carlos Reyes Pacheco
OCP
-------Original Message-------
From: oracle-l_at_freelists.org
Date: 07/29/04 14:25:41
To: 'oracle-l_at_freelists.org'
Subject: SHOULD WE ANALYZE 9.2 SYS tables?
I had a question about a problem with 9.2 V$ views where a RULE hint helped V$LOCK tremendously.
Someone suggested Analyzing the SYS tables. IS everyone doing that now or is there considerable reticence? I didn't get a much current information when I searched the FAQ or Google
Has anyone experienced a downside?
Is anyone doing some of the tables but not all?
Thanks
Larry Wolfson
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html'unsubscribe' in the subject line.
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