I read in one article, that if oracle
found there are more than 1 index can
be used for our query indicate by first
column in index, oracle will use the latest index.
except we directly use index hint in our query.
hopes this help
- Robert Freeman <robertgfreeman_at_yahoo.com> wrote:
> Thanks Cary... I've actually considered most of
> those already. This isn't my
> database, I'm coming in to help someone else. In
> this case, the database
> schema was accidentally dropped, and recovered from
> an export. I'm wondering
> if the import might have created blocks that are
> packed more densely and
> that this might be the cause of the problem. I'm
> told the parameters are the
> same, that the physical structure is the same, they
> are not using stored
> outlines and the SQL has not been changed. No
> patches have been applied, so
> it's apples for apples with the exception of the
> statistics and, possibly,
> the data density. They have some old stored
> statistics that they generated
> pre-schema drop that they are supposed to send me,
> so I'm going to look at
> that tomorrow and run a 10053 trace on one of the
> changed queries and see
> what I can find. I was just wondering if I could be
> missing something
> obvious..... Seems like that is just the way, it's
> the obvious things that
> get missed... :-)
>
> Thanks so much for your comments!
>
> RF
>
> -----Original Message-----
> Millsap
> Sent: Sunday, January 19, 2003 8:54 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Robert,
>
> Seven reasons I can think of include changes to:
>
> 1. Oracle instance parameter values (changes when
> you edit the
> parameters, whether in the stored "init.ora" way, or
> via ALTER SYSTEM or
> ALTER SESSION commands)
> 2. Database table and index statistics (changes,
> e.g., when you run
> dbms_stats.gather_database_stats)
> 3. System CPU and I/O statistics (changes, e.g.,
> when you run
> dbms_stats.gather_system_stats)
> 4. Database schema configuration (changes when you
> create/drop indexes,
> etc.)
> 5. Stored outlines (changes when you create or
> reassign outlines)
> 6. SQL text (changes when you manipulate the
> application SQL)
> 7. Oracle query cost model (changes when you upgrade
> or patch your
> Oracle kernel)
>
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
>
> Upcoming events:
> - 2003 Hotsos Symposium, Feb 9-12 Dallas
> - RMOUG Training Days 2003, Mar 5-6 Denver
> - Hotsos Clinic 101, Mar 26-28 London
>
>
> -----Original Message-----
> Freeman
> Sent: Sunday, January 19, 2003 1:24 AM
> To: Multiple recipients of list ORACLE-L
>
> Hey Ya'all... (still got my southern roots even up
> here in Chicago!)
>
> Anyone want to throw in some possible reasons why an
> execution plan
> might
> change for a given table query....This is on
> Oracle9iR2 on SUN. I've
> looked
> at the obvious causes:
>
> 1. Object has changed - Appears not to have changed.
> 2. Database parameters have changed - Appears that
> no parameters have
> changed.
> 3. Statistics (data volumes, distribution,
> cardinality, etc) have
> changed -
> Still looking into this, but the volumes have not
> changed dramatically
> even
> if they have changed.
> 4. Other physical database changes.
>
> None of these seem to apply. I've got a database
> that a few weeks ago
> were
> doing indexed
> lookups using a partitioned index on a partitioned
> table. Now, it seems
> that
> these queries
> are doing full table scans on this partitioned
> table. I'm still
> gathering up
> the details for the items above (e.g how much have
> the objects changed)
> and
> I'll probably run a 10053 trace on one of the bad
> queries to see what
> the
> optimizer is doing on Monday, but I'd like to just
> poll for some
> additional
> ideas. I *AM* getting partition elimination (thank
> goodness) but I've
> got
> two FTS on one partition of this table that are just
> killing it. They
> want
> to quantify the reason why this access has changed
> so I'm trying to
> think of
> what kinds of stuff I can look at to try to do this.
>
> I will add that this table was just rebuilt recently
> (through
> imp/exp)...
> can the change in row to block density make the
> difference.... hmmmm....
>
> Any ideas??
>
> RF
>
> --
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> Author: Robert Freeman
> INET: robertgfreeman_at_yahoo.com
>
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Received on Mon Jan 20 2003 - 06:26:56 CST
