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:
- Performance Diagnosis 101: 10/28 Phoenix, 11/19 Sydney
- SQL Optimization 101: 12/8-12 Dallas
- Hotsos Symposium 2004: 3/7-10 Dallas
- Visit www.hotsos.com for schedule details...
-----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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