Re: increasing COMPATIBLE parameter

From: Niall Litchfield <niall.litchfield_at_gmail.com>
Date: Wed, 25 Mar 2015 16:50:11 +0000
Message-ID: <CABe10sZqEvFsiOOph6AQHsERUT6QCMuTX5mA_HQnyUrUnY9XJg_at_mail.gmail.com>

Changing COMPATIBLE should not make any Optimizer changes. It's all about on disk storage. I can imagine there might be a few niche edge cases, but COMPATIBLE isn't fundamentally an optimizer thing.

The broad brush approach for the optimizer is "OPTIMIZER_FEATURES_ENABLE" and then there is individual control via FIX_CONTROL.

On Wed, Mar 25, 2015 at 3:47 PM, MARK BRINSMEAD <mark.brinsmead_at_gmail.com> wrote:

> I bet the database uses the optimizer though. :-)
>
> There are hundreds, maybe even thousands, of differences in the query
> optimizer between 10gR2 and 11gR2, and I expect the vast majority of those
> are suppressed when you run with COMPATIBLE=10.2.0.4
>
> You really should do a regression test before making this change,
> especially considering that it is a one-way thing. You can increase the
> value of COMPATIBLE, but you can *never* decrease it again. Not unless
> you are ready to do an export/import.
>
> Most likely, you will be perfectly okay. *LOTS* of people complete this
> upgrade without a hitch. But in the unlikely(?) case that you are not one
> of them, you'll probably want to show you did "due diligence" first.
>
> On Tue, Mar 24, 2015 at 5:15 PM, Sheehan, Jeremy <
> JEREMY.SHEEHAN_at_nexteraenergy.com> wrote:
>
>> It's been modified in a test instance for a few weeks but I didn't
>> change it. Someone else did and didn't document anything and they don't
>> remember if anything else was done. This is a very vanilla db. No ASM,
>> RAC.
>>
>> Thanks!
>>
>> Jeremy
>>
>> Sent from a phone
>>
>> *From:* Don Seiler <don_at_seiler.us>
>> *Sent:* Mar 24, 2015 4:55 PM
>> *To:* Sheehan, Jeremy
>> *Cc:* Oracle-L (oracle-l_at_freelists.org)
>> *Subject:* Re: increasing COMPATIBLE parameter
>>
>> This is an EXTERNAL email. Exercise caution. DO NOT open attachments
>> or click links from unknown senders or unexpected email.
>> ------------------------------
>>
>> I would be sure to test application behavior on a test/staging database
>> prior to doing this. But then again, that's solid advice for making any
>> change in a database.
>>
>> Sometimes behavior of various components can change with the compatible
>> parameter. I've seen it in ASM diskgroup compatible changes, for what its
>> worth.
>>
>> Don.
>>
>> On Tue, Mar 24, 2015 at 3:50 PM, Sheehan, Jeremy <
>> JEREMY.SHEEHAN_at_nexteraenergy.com> wrote:
>>
>>> Hello,
>>>
>>>
>>>
>>> I’m on 11.2.0.3 and am looking to update the COMPATIBLE parameter in a
>>> database from 10.2.0.4 to 11.2.0.3. I’ve searched pretty extensively (gone
>>> to page 3 of Google results and checked on MOS – 733987.1). Aside from
>>> taking a backup before making this change, are there any additional things
>>> I should look for or do after the change?
>>>
>>>
>>>
>>> Please let me know! Thanks in advance.
>>>
>>>
>>>
>>> Jeremy
>>>
>>
>>
>>
>> --
>> Don Seiler
>> http://www.seiler.us
>>
>
>

-- 
Niall Litchfield
Oracle DBA
http://www.orawin.info

--
http://www.freelists.org/webpage/oracle-l

Received on Wed Mar 25 2015 - 17:50:11 CET