Oracle-L: RE: Prevent FTS

From: <Govind.Arumugam_at_alltel.com>
Date: Mon, 06 Jan 2003 14:14:06 -0800
Message-ID: <F001.00527FE8.20030106141406@fatcity.com>

Please check Jonathan Lewis book 'Practice Oracle 8i'. This book provides lot more details about these two optimizer related parameters that could significantly affect FTS situations.

optimizer_index_caching
optimizer_index_cost_adj

The general 'harmless' guidelines could be setting 10 to optimizer_index_caching and 35 to optimizer_index_cost_adj.

HTH. Govind

-----Original Message-----
Sent: Monday, January 06, 2003 2:49 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: <Govind.Arumugam_at_alltel.com
INET: Govind.Arumugam_at_alltel.com

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