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Re: Question re System Statistics

From: LS Cheng <>
Date: Sun, 17 Jun 2007 09:59:07 +0200
Message-ID: <>

Hi Brandon

I was wondering how much time do you gather system statistics, a couple of hours per day? Peak time perhaps?



On 6/15/07, Allen, Brandon <> wrote:

> The point of system stats is to give the CBO the most accurate
> information about the CPU and I/O performance of your system so I'd say
> it's only necessary to gather new system stats whenever the performance
> of your system changes so, e.g. if you make any hardware changes,
> signficant code changes (e.g. add/remove/patch/upgrade an application),
> or load changes (e.g. add/remove a significant amount of users or
> transactions).
> I like to gather my stats over several "typical" business days and then
> average them and manually set my system stats to the average values
> during a typical load. Of course if you have wide variations in load,
> e.g. OLTP by day and batch/OLAP/DSS by night, then you might want to
> switch between two different sets of stats (set a job to do this
> automatically).
> Aside from gathering new system stats after significant changes to the
> system, I think a good approach is to periodically (maybe quarterly?)
> gather your system stats in a staging table, and then compare those to
> your system stats that are currently in effect and investigate any major
> differences and then update your real system stats if warranted by the
> results of your investigation.
> HTH,
> Brandon
> -----Original Message-----
> From:
> [] On Behalf Of William Wagman
> I would be interested in folks thoughts about how frequently system
> statistics should be gathered
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Received on Sun Jun 17 2007 - 02:59:07 CDT

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