caught out a lot of DBAs - even experienced ones...
John Kanagaraj
-Original Message-
From: Mohammad Rafiq [mailto:[EMAIL PROTECTED]]
Sent: Saturday, August 18, 2001 10:00 AM
To: Multiple recipients of list ORACLE-L
Subject: RE: Q about Oracle Optimizer
Anita,
You are 100% right for your
of list ORACLE-L
Subject: RE: Q about Oracle Optimizer
Anita,
You are 100% right for your explanation. I observed that
behaviour just last
week when we migrated our second production database from 7.3.4.5 to
8.1.6.2 and my colleague forgot to define optimizer as rule in our new
init.ora file
That's true provided you're not using any of the new
features introduced in 8.0, and later versions, that
automatically cause the CBO to be used (e.g.
partitioning, degree or instances 1, IOT, etc...)
When in doubt, I always check metalink note: 66484.1.
HTH,
-- Anita
--- Jon Walthour [EMAIL
IMHO,Problem in this situation is that ,in 7.3.4 ,if I am not wrong ,thier
optimizer must be RULE as default and after migration if optimizer is not
explicitly set as RULE , default optimizer in 8.1.6 is CHOOSE. This is the
reason their objects never analyzed in 7.3.4 or now in 8.1.6.
If
Anita,
You are 100% right for your explanation. I observed that behaviour just last
week when we migrated our second production database from 7.3.4.5 to
8.1.6.2 and my colleague forgot to define optimizer as rule in our new
init.ora file and resultantly optimizer became CHOOSE and from very
It simply uses RBO instead.
g
-Original Message-
Sent: Thursday, August 16, 2001 9:46 AM
To: Multiple recipients of list ORACLE-L
Hi list,
a quick question about oracle optimizer.
a customer has database migrated from 7.3.4 to 8.1.6 on AIX. Data was
transfered via full exp/imp.
Volker:
If optimizer_mode = 'choose', then the optimizer chooses between
cost-based optimization and rule-based optimization based on whether or
not statistics are present. In your case, since they aren't it's using
rule-based.
-Original Message-
Volker
Sent: Thursday, August 16, 2001
If the objects in a query have not been analyze, then rule mode is
defaulted.
If there are objects in the database which are analyze, yet the tables you
are using are not analyzed, rule mode will still be used.
If one table is analyzed, and it is joined with 5 others which are not
analyzed,
