Re: Physics of the FILTER operation within SQL_PLANE.
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 30 Jun 2004 09:42:22 +0100
Your observation is absolutely true.
You don't even have to use two separate queries
to demonstrate the point, all you have to do is
change the sql*plus arraysize on a simple
select non-indexed_column
from table
where primary_key between X and Y
If you check v$sql, you will see that the
LIO count goes up as the arraysize goes down.
Identifying statements with high LIO counts is
a necessary, but not sufficient, tuning exercise.
Identifying statements with high PIO counts is
a necessary, but not sufficient, tuning exercise.
Identifying statements with high CPU usage
is a necessary, but not sufficient, tuning exercise.
Identifying statements that do a lot of sorting
is a necessary, but not sufficient, tuning exercise.
Identifying statements with a high-latch impact
is a necessary is another necessary, but not
sufficient, tuning exercise in a system with a
high degree of concurrency.
I could go on - but I'd be sure to miss a few.
It's usually relatively easy to spot the big hitters,
whatever you do, and work out how to fix them.
But the point does come where the ONLY possible
way to do trouble-shooting is to breathe down the
neck of someone who has a complaint, and watch
what the system does as they go through the task
that giving them grief. i.e. Cary's 10046 approach.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/seminar.html
Optimising Oracle Seminar - schedule updated May 1st
----- Original Message -----
From: <J.Velikanovs@xxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Tuesday, June 29, 2004 10:45 AM
Subject: Re: Physics of the FILTER operation within SQL_PLANE.
One important conceptual personal conclusion I got from this
investigation:
vvvvvvvvvvvvvvvv
We can't compare two SQL executions plans (for one query) efficiency by
BUFFERs gotten (LIO) executing query.
^^^^^^^^^^^^^^^^
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