Re: Does primary key structure impact UPDATE performance?
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 17 May 2004 21:37:17 +0100
If the excess CPU were to do with undo being
applied, all the undo blocks visited would also
be recorded under the "query" count for the
fetch.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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----- Original Message -----
From: "Tanel Põder" <tanel.poder.003@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Monday, May 17, 2004 4:47 PM
Subject: Re: Does primary key structure impact UPDATE performance?
Assuming, that you're running on decent CPUs, it seems strange that 2371
consistent reads and 1 current read require 1,72 seconds of CPU time (even
in the very unlikely event when CPU usage between every physical IO would
heve been overaccounted due quantization error).
This PL/SQL loop, does it open a cursor and keep it open for a long time?
That way several rollback segment block gets might be required to satisfy a
consistent read, that could explain high CPU usage per LIO in extreme cases.
(But it wouldn't explain why there is such a difference between two tables
w. different indexes).
Maybe query definitions + execution plans would give some more clues...
Tanel.
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