RE: Skip scans
- From: "Parker, Matthew" <matthewp@xxxxxxxxxx>
- To: <mgogala@xxxxxxxxxxxxxxxxxxxx>, "Oracle-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 30 Dec 2004 00:53:11 -0800
In 9i skip scan is turned on automatically without the necessity of the =
hint. Under 9.2.0.3 we had to turn it off as the optimizer was choosing =
it when other more usable indexes were avaialable. In 9.2.0.5, it =
appears more stable. However, for simple performance it is useful in low =
usage scenarios, (the query is not executed that often and you don't =
have space to burn). Under heavy usage it is much more efficient to =
simple build the index you need versus incurring the block buffer hit =
from the skip scan.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx =
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Mladen Gogala
Sent: Wednesday, December 29, 2004 10:47 AM
To: 'Oracle-L (E-mail)'
Subject: Skip scans
Is anybody using index skip scan feature? What would be a situation in =
which the feature should be used? I have a SQL statement, part of ETL =
process that I have to tune. The initial reuslts are encouraging =
although not dramatic. Does anybody else have any type of practical =
experience with skip scans and index_ss hint?
--
Mladen Gogala
Oracle DBA
Ext. 121
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