Re: Oracle Database Resource Manager
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 3 May 2004 21:49:26 +0100
Notes in-line.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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----- Original Message -----
From: "Pete Sharman" <peter.sharman@xxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Cc: "Peter Ross Sharman" <PETER.SHARMAN@xxxxxxxxxx>
Sent: Monday, May 03, 2004 8:27 PM
Subject: RE: Oracle Database Resource Manager
I don't know who the instructor was, but he or she is talking crap (pardon =
my French). Really, what would be the point of implementing a resource man=
ager that itself takes too many resources?
[jl] Good question - I asked myself the same thing when
[jl] I first ran the 9.0.1 resource manager on my HP-UX
[jl] box. Under some conditions the overhead was about
[jl] 100%. Things improved when the sampling rate was
[jl] dropped somewhat.
One thing that people get confused about with the Resource Manager, BTW, is=
when it actually takes effect. It's when the resource being managed is ex=
hausted i.e. if you're allocating different amounts of the CPU utilization =
to different groups, you WON'T see Resource Manager kick in until CPU utili=
zation hits 100%. After all, it's not a problem till then, right?
[jl] I've found that it tends to kick in only after the demand
[jl] exceeds about 200% of available resources; and then
[jl] the allocation fractions aren't obeyed particularly well.
[jl] One of the positive things about it though is that you
[jl] can set it up to error out any SQL whose calculated
[jl] cost exceeds a given limit - which means less of the
[jl] 'query from hell' stuff wrecking performance for
[jl] everyone else on the system.
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