12.1.0.2 comes with 2 very bad parameters that are almost universally
instructed to set from the defaults.
Optimizer_adaptive_plans & optimizer_adaptive_features
(Disclaimer: there's been a lot of changes in this area in 12.1 and Oracle
backported a patch from 12.2 to fix it and further granularlize the
adaptive features so I may have the parameter names a bit confused)
Anyway Oracle issued guidance for 12.1 and the adaptive features found here:
[image: My Oracle Support Banner]Recommendations for Adaptive Features in
Oracle Database 12c Release 1 (Adaptive Features, Adaptive Statistics & 12c
SQL Performance) (Doc ID 2187449.1)
HTH
Chris Taylor
(P.S. I cannot recommend strongly enough to go immediately to 12.2 and get
off 12.1!)
On Thu, Sep 12, 2019, 8:57 PM kunwar singh <krishsingh.111@xxxxxxxxx> wrote:
Thanks Mladen for the response.
Yes , i have tried to pretty much everything under the sun with the
statistics, histograms, dynamic sampling.
On Thu, Sep 12, 2019 at 9:52 PM Mladen Gogala <gogala.mladen@xxxxxxxxx>
wrote:
On 9/12/19 9:43 PM, kunwar singh wrote:
Hi Listers,Have you tried with different statistics options? System statistics,
Silly question :)
Is there any Oracle guru who give course on this specific topic and
goes much in depth.
Not looking for course on sql tuning. I am able to tune the query in
most cases, it is the optimizer decisions for many queries in a new
version upgrade(11g to 12.1.0.2).. which are giving me some headaches
as many applications we support generate queries dynamically and
statistics optimization is the farthest i am able to go to get good
plans.
Cannot use SPM options due to dynamic nature of sqls generation.
OPTIMIZER_DYNAMIC_SAMPLING, proper histograms and alike? I found out
long time ago that collecting statistics properly usually gives me good
performance for 99% of the queries. The best way to tune is not to do
it at all.
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
--
//www.freelists.org/webpage/oracle-l
--
Cheers,
Kunwar
