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Chris Saxon

Thanks for the question, Sagar.

Asked: May 12, 2016 - 3:48 pm UTC

Last updated: May 12, 2016 - 4:20 pm UTC

Version: 12.1.0.2.0

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You Asked

Hi Tom,

I wanted to check your views regarding MoS ID: 2033658.1.
If customer is indeed facing performance issues with functional queries in 12c (12.1.0.2.0) PDB configuration which was not the case before upgrading to 12c from 11.2.0.4.0 version, and issue is traced to slow performance of data dictionary views - is it safe to modify the hidden parameter "_common_data_view_enabled" value to FALSE?

I know modifying the hidden parameter's value is strongly not recommended and is tinkering with OOTB functionality, but how can one circumvent around such issues?

Many Thanks....

and Chris said...

The note also says:

"Upgrade to 12.2 or request patches for unpublished bugs 16306918 and 17861949."

You can't quite upgrade to 12.2 yet :)

So I would recommend requesting the patches first.

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Comments

Sagar Dua, May 12, 2016 - 4:06 pm UTC

Thanks for the prompt response Chris.
Yes I saw the note :)

You're right, request for patch will be the first thing I would also advice.

Just wanted to check the side effects of modifying that parameter (if it was required), as I got nothing for it on my web search.
Chris Saxon
May 12, 2016 - 4:20 pm UTC

Well it's an undocumented parameter, so it's unlikely you'll find much!

Again, as the note says:

"This allows the optimizer to override the common view and access the data through dictionary tables residing in the respective pluggable database only."

So these will only see information from the specific PDB. This will limit functionality. Precisely what this means will change over time as you patch/upgrade. Even if it works now, you may find yourself in a sticky mess when you go to 12.2. Or 13.1. etc.
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