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Re: Explain Plan

From: Niall Litchfield <niall.litchfield_at_dial.pipex.com>
Date: Fri, 4 Feb 2005 21:03:47 -0000
Message-ID: <4203e324$0$19158$cc9e4d1f@news-text.dial.pipex.com>


<amerar_at_iwc.net> wrote in message news:1107548968.828618.55110_at_l41g2000cwc.googlegroups.com...
>
> Actually you are wrong. We are using Locally Managed. And again,
> there is nothing wrong with the explain plan I displayed.
>
> What I am asking for is how or where I can find info on understand that
> hunk of junk.

Sybrand was correct about the reference manual - the performance tuning guide does tell you about access methods, types of join etc. http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96533/toc.htm is the reference, you'll see it tells you about access paths and join methods, about explain plan and about tkprof. Its the place to start.

In *general* you read inside out with the results of the inner operation providing the input rowset for the outer operation. If you are running TKPROF with the explain= parameter don't, the plans it gives are those that would be executed if the statement ran now in the environment as it is now for the user you use to explain it. The only way to get the plan that actually was executed is to use the STAT lines (which is what tkprof does if you don't use explain= ) in the trace file or to query v$sql_plan if you have that view in the version you are running.

-- 
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com
Received on Fri Feb 04 2005 - 15:03:47 CST

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