Oracle-L: RE: Prevent FTS

From: Fink, Dan <Dan.Fink_at_mdx.com>
Date: Mon, 06 Jan 2003 14:14:05 -0800
Message-ID: <F001.00527FCD.20030106141405@fatcity.com>

Go to http://www.evdbt.com/papers.htm and read "The Search for Intelligent Life in the Cost-Based Optimizer" and "How to Improve Database Performance Using Full Table-Scans". They have very good explanations about the situation you are facing. They are also excellent reads!

-----Original Message-----
Sent: Monday, January 06, 2003 12:49 PM
To: Multiple recipients of list ORACLE-L

What is the significance of parameter OPTIMIZER_INDEX_COST_ADJ ? When I tried to change the value the explain plan has changed .

alter session set OPTIMIZER_INDEX_COST_ADJ = 10

table access for Z was by index rowid

alter session set OPTIMIZER_INDEX_COST_ADJ = 100

table access for Z was full

How can I make effective use of this parameter . If i dont want to use this in alter session,can this value be set elsewhere.
what is the difference between setting this parameter to some other value than
default
compared to using hints in sql stmt.
I've tried some hints like rowid,index but it did not work for the join stmt as it still used the FTS of Z before I tried to change the above parameter to
10.

-----Original Message-----
Sent: Monday, January 06, 2003 11:03 PM
To: 'ORACLE-L_at_fatcity.com'

Hi All,

I've 3 tables table x,y,z
pk of x is (col_1,col_2),pk of y is (col_1,col_2,col_4,col_5),pk of z is (col_1,col_2)

where clause is :

where x.col_1 = y.col_1

and x.col_2 = y.col_2
and x.col_1 = z.col_1
and x.col_2 = z.col_2
and y.col_1 = z.col_1
and y.col_2 = z.col_2

and x.col_3 in ('val1','val2','val3')
and.....
..

Explain plan shows that there is a FTS of table z . what can be the reason for this and how to prevent this.

Thanks
Manoj

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Author:
INET: manoj.gurnani_at_orbitech.co.in

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Author: Fink, Dan
INET: Dan.Fink_at_mdx.com

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