Re: increasing COMPATIBLE parameter
- From: MARK BRINSMEAD <mark.brinsmead@xxxxxxxxx>
- To: Carlos Sierra <carlos.sierra.usa@xxxxxxxxx>
- Date: Wed, 25 Mar 2015 14:55:38 -0400
Ah. I see the objection, reading farther down the thread.
Okay. I was only *guessing* that COMPATIBLE would probably affect
optimizer features -- in addition to many others. While it turns out that
the example/suggestion I have given -- about optimizer issues resulting
from changing COMPATIBLE -- is probably fatuous, this does not really
affect the discussion.
Changing COMPATIBLE from 10.2.0.3 to 11.0.2.4 *might* have unpredictable
affects on the application. It is a one-way change that cannot be reverted
without rebuilding the database. It is therefore prudent to test carefully
before making the change.
My apologies to all for a poor choice of illustrations. :-)
On Wed, Mar 25, 2015 at 2:49 PM, MARK BRINSMEAD <mark.brinsmead@xxxxxxxxx>
wrote:
> Yes. I know what COMPATIBLE is for. :-)
>
> But the *intended* use of COMPATIBLE is not what is being discussed here.
>
> On Wed, Mar 25, 2015 at 12:16 PM, Carlos Sierra <
> carlos.sierra.usa@xxxxxxxxx> wrote:
>
>> Mark,
>>
>> COMPATIBLE is used when you do a database upgrade, lets say from 10.2.0.4
>> to 11.2.0.4, and you need (for a few days) to have the capability to go
>> back to 10.2.0.4. Once you are comfortable on the new release, you simply
>> reset this parameter and let it default for current database release you
>> are on.
>>
>> OPTIMIZER_FEATURES_ENABLE controls many features of the CBO, thus you can
>> set it to a prior value when and if needed. I only see some value to do
>> this during a few days after an upgrade. For the most part, you also want
>> to reset this parameter (remove from SPFILE) and use default value so you
>> get to benefit of the new features for your release.
>>
>> So if you are on 11g, and have been on it for a while, I do not see any
>> reason to keep COMPATIBLE set to a prior version. It is not like you will
>> downgrade to this prior version anymore. So I would simply reset it (remove
>> from SPFILE) and let it default. Yes, you cannot go back to the outdated
>> value you had. But again, do you still want to go back to your old release?
>>
>> Please, corrections are always welcomed.
>>
>> Carlos Sierra
>> Life is Good!
>>
>>
>>
>> On Mar 25, 2015, at 11:47, MARK BRINSMEAD <mark.brinsmead@xxxxxxxxx>
>> 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@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
>>> *Sent:* Mar 24, 2015 4:55 PM
>>> *To:* Sheehan, Jeremy
>>> *Cc:* Oracle-L (oracle-l@xxxxxxxxxxxxx)
>>> *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@xxxxxxxxxxxxxxxxx> 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
>>>
>>
>>
>>
>
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