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Re: Timed_statistics

From: Connor McDonald <connor_mcdonald_at_yahoo.com>
Date: Thu, 17 Oct 2002 23:28:20 +0100
Message-ID: <3DAF3984.76D8@yahoo.com>


Jonathan Lewis wrote:
>
> Is 8.1.7.2 the version where switching on
> timed_statistics has the odd side effect of
> stopping shareable SQL from being shared
> in certain circumstances. The consequence
> of an extreme attack of that would be a flooded
> shared pool and death by library cache latch
> contention.
>
> Try taking snapshots of v$latch in the five
> minutes before, and the five minutes after
> switching on timed_statistics - ditto
> v$system_events (which will, of course,
> only give you the count of waits in the
> before snapshot).
>
> --
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> Next Seminar dates:
> (see http://www.jlcomp.demon.co.uk/seminar.html )
>
> ____USA__________November 7/9 (Detroit)
> ____USA__________November 19/21 (Dallas)
> ____England______November 12/14
>
> The Co-operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
> Norman Dunbar wrote in message ...
> >Evening all,
> >
> >I've got a 'friend' who has a database at 8172 on a SUN box.
> >This database is having some preformance problems.
> >Running Statspack snapshots every half hour is fine.
> >Doing it with timed_statitics = true is absolutely screweing
> (technical
> >term) the database.
> >Response times plummet, users complain etc etc.
> >
> >I've never had any problems with T_S before myself, and I'm a bit
> >stumped as to why the severe effect with this database.
> >We know that there is a (serios) disc I/O problem (top wait is for 90
> >mins out of an 8 hour uptime on 'db file sequential read') but CPU is
> >mainly idle (8 processors, 2GB RAM).
> >Discs are RAW and I've got him checking if it is software mirroring
> or
> >not, and if so is DIRTY REGION LOGGING on, and if so, where are the
> >logging files (Thanks for that one Jonathan - last year at the Belfry
> !)
> >
> >Any pointers please - the info from T_S is much better than without
> it,
> >but it is almost impossible to turn it on for long.
> >
> >
> >Cheers,
> >Norman.
> >
> >-------------------------------------
> >Norman Dunbar
> >Database/Unix administrator
> >Lynx Financial Systems Ltd.
> >mailto:Norman.Dunbar_at_LFS.co.uk
> >Tel: 0113 289 6265
> >Fax: 0113 289 3146
> >URL: http://www.Lynx-FS.com
> >-------------------------------------
> >

(Theoretically) ie what they pumped out on Metalink, it was 8.1.5.x, 8.1.6.0 and 8.1.6.2, all slightly differents variations on a theme (some only occurred if sql_trace was also one etc etc).

We're running T_S on a bunch of HP-UX 11 boxes here at work with no ill effects oberserved

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."
Received on Thu Oct 17 2002 - 17:28:20 CDT

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