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Re: URGENT! Writes to Disk while Doing a SELECT statement?

From: Jurij Modic <jmodic_at_src.si>
Date: Wed, 03 Feb 1999 16:09:54 GMT
Message-ID: <36b87284.9700545@news.siol.net>


On Wed, 03 Feb 1999 08:06:47 GMT, Satar <satar_at_my-dejanews.com> wrote:

>Please Help...
>Situation:
>Test Server running Oracle 7.3.4.0.1 on Solaris 2.6 release 5/98.
>I'm the only one logged in on the server and database.
>Sun E450 Server attatched to a A5000. (software Raid 0+1).
>
>I'm observing the I/O of the Sun E450 Server. I do a Basic select on a view
>(which is join of 5 tables). It is a basic select with no sorting (no Order
>by). I notice that three of my datafiles are being written to: rbs, temp, and
>my data datafile.
>
>My question:
>What is going on? What is Oracle doing? Why did I see write activity (every
>time) and no Read activity (Maybe there was Read activity only the first time
>running the SELECT statement?).

Are you sure there is no sorting with the select? It's not just ORDER BY that can causes sorting. The most probable candidates are GROUP BY in your view or perhaps a MERGE JOIN used in a join. Run an EXPLAIN PLAN and look for any implicit SORT operation.

>Regards,
>Satar
>Oracle DBA/UNIX System Admin
>"Opinions are the result of the voices in my head only,
>and do not reflect my employer or Oracle Corporation."

HTH,
Jurij Modic <jmodic_at_src.si>
Certified Oracle7 DBA (OCP)



The above opinions are mine and do not represent any official standpoints of my employer Received on Wed Feb 03 1999 - 10:09:54 CST

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