Re: optimizer_features_enabled
- From: Paul Drake <discgolfdba@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Thu, 19 Aug 2004 19:26:39 -0700 (PDT)
--- Mark Burgess <mburgess_nz@xxxxxxxxxxx> wrote:
> Hi,
> I have a question around the
> optimizer_features_enabled parameter. If we set this
> parameter to 8.1.7 in a 9.2 database does the RDBMS
> kernel use 8.1.7 optimization algorithms only or
> does
> it use the 9.2 optimization algorithms but limit the
> CBO to only using 8.1.7 CBO features?
> Any clarification on this would be much appreciated.
> Regards,
> Mark
Wolfgang presented at Hotsos in March covering this
briefly - or maybe I just tried to pin him down on
this afterwards. I don't quite recall.
Check out his paper "whats new in the 9i CBO".
You can possibly find these docs at hotsos:
What is new in the Oracle 9i CBO.pdf
Using DBMS_STATS in Access Path Optimization.doc.pdf
SQL Tuning with Statistics.pdf
Wolfgang refers to this note:
http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_database_id=NOT&p_id=62337.1
Reference Note for Init.Ora Parameter
"OPTIMIZER_FEATURES_ENABLE".
here is one tasty tidbit:
Parameter:optimizer_dynamic_sampling
(1 if >= 9.2.0, 0 otherwise)
o_f_e = 8.1.7 is a like tourniquet.
its a last resort.
if you apply it, you will lose the limb.
You will be too risk averse to remove it.
Where I applied it, we're not coming off of it until
the testing cycle for 10.1.
I can tell you that for Standard Edition,
function-based indexes still work with o_f_e=8.1.7,
but that is likely due to FBIs being available in
Enterprise Edition in 8.1.7.
good luck.
Pd
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