Try to reduce High Water Mark on your table by
creating as select a backup table
truncate original table
insert into original table from backup table...
This is based on your info for full table scan...Please also rebuild indexes
on that table and analyze table if you are on COST BASED..
HTH,
Regards
Rafiq
Reply-To: [EMAIL PROTECTED]
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
Date: Wed, 06 Feb 2002 13:45:44 -0800
Hi, Bill
You are right, there is really something to do with the index.
I drop&re-created that PK index, it became much faster, but after 5 minutes,
it became slow again, and I am sure no records insert/delete/update
happened. I drop&re-created that indexes again, nothing happened this time,
it is still slow!
It is really weird!
And I found on the bad performance database, a simplest query: select
count(*) from table_name will take 4 seconds!
the explain_plan said it used cost-optimizer, using fast_full_index_scan on
that PK index,
what should I do with the index? I already tried to re-created the PK index.
The bad performance database is on a super-box, 4 CPUs and more memory. the
good performance one is on a normal box.
And the table and index is analyzed at same way.
thanks a lot for your reply.
Kevin Wang
----- Original Message -----
From: Bill Zakrzewski
To: kevin wang
Sent: Wednesday, February 06, 2002 12:38 PM
Subject: Re: question on EXPLAIN_PLAN
Kevin,
Have these indexes been rebuilt recently? If not, you may want to
consider rebuilding the indexes. Not sure if this is your issue, but if you
have inserted/deleted records from your tables over time, the index levels
may have grown as well.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Bill Zakrzewski
Senior Consultant
Intactus Technology, Inc.
----- Original Message -----
From: kevin wang
To: LazyDBA.com Discussion
Sent: Wednesday, February 06, 2002 2:43 PM
Subject: question on EXPLAIN_PLAN
Hi, guys
The problem belows is really make me confused and gave me big
trouble, is there someone can give me some hlep?
I have two databses, same version(oracle 8.1.6),same O/S(win2000),
same schema structure, different data(but small difference of size).
and even exactly same explain_plan of my sql query.
But on one database, the cardinality of one PK index access upon one
table is 27(cost=2,card=27,bytes=756) (table rows 263758)
and the other is 11706!!!! (cost=3,card=11706,bytes=199002)( table
rows 351173).
so, on one DB the sql query took 300ms, one the other, it took 5
seconds!
Any advise is highly appreciated.
thanks,
Kevin Wang
Database Administrator
Vivonet Canada Inc.
MOHAMMAD RAFIQ
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