Re: Query Performance with params

Hello Ram,

Rule #1: Do not set OPTIMIZER_INDEX_CACHING & OPTIMIZER_INDEX_COST_ADJ
Rule #2: If Rule #1 does not apply - Do not set OPTIMIZER_INDEX_CACHING & OPTIMIZER_INDEX_COST_ADJ
Rule #3: Analyze the root cause why the indexes are not used

Rule #1 & #2 are the most important ones here. There are only a few cases when to set these parameters like suggestions from 3rd party software vendors (e.g. SAP or E-Business).

There are so many reasons (e.g. clustering factor, predicates, correlation, etc.) why an index may not be used - so guessing would be not very productive here. Get the query and a CBO trace and check the reason.

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website: http://www.soocs.de
Twitter: _at_OracleSK
Upcoming online seminar: http://tinyurl.com/17-06-13-Shared-Pool-Internals

> Ram Raman <veeeraman_at_gmail.com> hat am 29. April 2017 um 21:23 geschrieben:
>
> List,
>
> We have a 12c db that runs an ERP app. We face slowness with some processes - Upon analysis we created some indexes and re ran the processes. A few
> of the processes would not complete - the optimizer would not use the index. We adjusted the OIC/OICA (idxCachg/idxCostAdj) - with new values
> several of the reports completed. However some other processes do not complete even after an hour. But they complete ok with the older values of
> oic/oica. Many of the SQLs are generated dynamically, so using hints is not an option.
>
> It looks like we can work with adjusting the values of oic/oica for different processes. However many of these users could run the processes at the
> same time. My limited research shows that oic/oica have an effect on the access paths and eventually the cost of the query; read wolfgang's paper on
> the subject. I am sure I am not the only person who faced this problem. Any ideas on how to approach the issue? Thanks a lot.
>
> Ram.
 

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