Oracle-L: RE: DB Parameters

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Thu, 09 Oct 2003 06:49:36 -0800
Message-ID: <F001.005D28FC.20031009064936@fatcity.com>

Walid,

It's unlikely that a database parameter will provide the solution to your problem.

Trace the DELETE if you can (DBMS_SUPPORT.START_TRACE_IN_SESSION), to see what's taking so long. Odds are that your DELETE is poorly optimized SQL that's simply doing more work than it needs to be doing. BUT FIND OUT BEFORE YOU ASSUME THAT'S WHAT IT IS. If you find that your DELETE is consuming massive amounts of CPU service or OS read time, then take the query part of your DELETE out of your DELETE statement, and work with it until you get a decent execution plan. For example, if your statement were:

	DELETE FROM table
	WHERE predicate-list

...then focus on optimizing the query

	SELECT rowid FROM table
	WHERE predicate-list

At this point, it's a standard SQL optimization exercise. The tools at your disposal include, but are not restricted to:

Can you use TRUNCATE to produce a functionally correct end-state?
Are the statistics on your table reasonable?
Does your SQL use all the join conditions that are necessary to allow the Oracle Query Optimizer to do its job of finding the best plan?
Does your table have all the check constraints on it that the Oracle Query Optimizer needs to do its job of finding the best plan?
Do the indexes exist that the Oracle Query Optimizer needs to do its job of finding the best plan?
Can you eliminate unnecessary indexes without harming other SQL statements?
And so on...

As a last resort, you might consider using hints upon the SQL to coax the optimizer into using the plan you want, but I would advise doing this only in unusual circumstances. If all your other work is done properly, then I would submit that it's usually a good idea to eliminate hints from your SQL.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

Upcoming events:
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-----Original Message-----
Walid Alkaakati
Sent: Thursday, October 09, 2003 3:29 AM To: Multiple recipients of list ORACLE-L

Hi List ,

Can you help me please ,

What are the database parameters that i have to increase or modify in order to increase the speed of my ddl
statments ,i have a statment that delete a table with 40000 record but it
takes about nine hours to accomplish !!!

Is their any parameters on the server that i have to check ??,Increase
rollback segment is not helpfull at all . Iam running oracle 9.2.0.1.0 production .

Thanks for your help.

Bye.

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Received on Thu Oct 09 2003 - 09:49:36 CDT