Ferenc,

Looks like you got your way with the result. Depressing but true
What happened to your web site, is it still up and if so what is the URL

Regards

John


-----Original Message-----
Sent: 25 June 2002 13:33
To: Multiple recipients of list ORACLE-L


Mike

Siebel does not support CBO either, and I have seen your exact problem.

If you have the segment level degree of parallelism on any of the tables or
indexes in the query with a non serial degree of parallelism, the optimizer
immediately invokes CBO for the query, regardless of what optimizer_mode is
set to, and of course in the absence of statistics, a query written for CBO
will stink like nothing stinketh, especially on large data set. I tore my
hair out for a day with such a query at a customer's site, and like you, all
I could say is 'ba-a-a-a-a-a-a'. But I will never forget it.

I'd love to chat more, but the game is about to start, and I want to see
Germany hand justice to Korea, though it will be difficult because the
Germans only have 11 players, and the Koreans up to now have had 14 on the
field (team plus ref plus two lines men ). At least I have my priorities
straight.

Hope that helps you.

Regards:
Ferenc Mantfeld
Senior Performance Engineer
Siebel Performance Engineering
Melbourne, 3000, VIC, Australia
Only Robinson Crusoe had all his work done by Friday


-----Original Message-----
Sent: Monday, 24 June 2002 4:34 PM
To: Multiple recipients of list ORACLE-L


Hi All:

Here's a strange thing.  I did a reorg of a very nasty tablespace
over the weekend.  I broke it out into 4 new tablespaces for the
large tables and the rest into a single tablespace.  This database
has 'optimizer_mode = rule' set in the initSID.ora file because
the Cognos application can't seem to handle the CBO, so I did
not compute any statistics as part of the process.

Sounds like routine maintenance, right?

Nope.  It went weird.  One query, which included an outer join
and a sub-query went from about 2 minutes to not finishing in
over two hours.  All indexes and objects were back in the DB.  I
verified that about a dozen times, all with manglement breathing
down my neck.  I EXPLAINED the query till I was blue in the face.
I rebuilt (again!) all the indexes.  No joy.

Finally, I thought "oh heck...might as well analyze them".

Shazzam.  Back to 2 minutes.  Huh?  But Optimizer-mode is RULE!!

How?  Why?  I look stupid and so does my whole DBA group.
Does anybody have any insights about this behavior?

Thanks,
Mike

---
===========================================================================
Michael P. Vergara
Oracle DBA
Guidant Corporation

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