Re: explain plan, can you explain this?

From: Luis Fernando Cerri <>
Date: Fri, 11 Jan 2008 14:25:07 -0300
Message-ID: <>

You are definitely right, Brandon.

By the way, it is very easy to understand all STATS$% tables and DBA_HIST% views and what information is stored in each one of them.

After that it becomes very simple to write a set of scripts to calculate deltas between each snapshot between a begin/end date/time and plot these deltas in a timeline graphic, using your preferred spreadsheet software.

I've been doing this for a while and these graphics really simplified my performance diagnostics work.


2008/1/11, Allen, Brandon <>:
> Andrew, the instances you've seen are normal. I think there is just some
> confusion here about exactly what we're all trying to say so I'll try to
> clarify:
> Yes, the statistics values stored in statspack and awr snapshots are
> cumulative, however the values reported by spreport.sql and awrrpt.sql (or
> by the "View Report" action under Snapshots in OEM) are the deltas
> calculated as the difference between those cumulative values for the
> specified begin and end snapshots.
> For example, at snap #1, we have accumulated 100 phyrds and at snap #10 we
> have accumulated 1000 phyrds, so when we run spreport or awrrpt and specify
> beginning snapshot #1 and end snapshot #10, it calculates the delta as
> 1000-100=900 and reports that 900 phyrds occurred during the interval
> between whatever time snapshots 1 and 10 were taken.
> Hopefully that makes sense and settles the issue so we can all get along now
> and enjoy our weekend :-)
> Regards,
> Brandon
> ________________________________
> From: []
> On Behalf Of Andrew Kerber
> well, unless I have run into 3 really strange instances, it looks like
> cumulative values to me. Unless you can explain why the phyrds and phywrts
> are higher for each snap than the previous one for every file in my
> instance.
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Received on Fri Jan 11 2008 - 11:25:07 CST

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