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Re: Any thoughts?

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 5 May 2004 00:10:12 +0000 (UTC)
Message-ID: <c79bd4$jh$1@sparta.btinternet.com>

Note in-line

-- 
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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"Igor Racic" <igor.racicC_at_freesurf.fr_no_C> wrote in message
news:40980203$0$13079$636a15ce_at_news.free.fr...

>
> Hi, Jonathan
>
> Many times in your book, posts on newsgroups and articles
> on the web I ask myself "How he found that thing ?" (I hope I'm note the
> only one :-) )
>
Most of the consultancy work I get has to deal with odd behaviour that needs a solution rather than a quick fix. This means I get to see more anomalies than most, and often have to investigate why they are appearing. Then in my spare time I just dig around and experiment a lot.
> Just curious here, what would be the reason that you will trust more
> this statistic over another one ?
>
History and consistency. consistent reads and db block gets have always shown odd anomalies when observed closely. v$buffer_pool_statistics appeared and contradicted v$sysstat quite dramatically. v$latch (cache buffers chains) frequently indicated that the figures in v$sysstat were suspect. sum(x$kcbsw) always seemed to be very close to the value for 'session logical reads'. Of course - this begs the question of what a session logical read is; or perhaps defines it as a type of buffer access that is recorded in x$kcbsw.
Received on Tue May 04 2004 - 19:10:12 CDT

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