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Re: Automatic Undo Managment on 9i

From: Pete Sharman <peter.sharman_at_oracle.com>
Date: 19 Dec 2002 10:47:45 -0800
Message-ID: <att48h03oq@drn.newsguy.com>


In article <3E00BB1A.2345C019_at_exesolutions.com>, DA says...
>
>Timmy Sin wrote:
>
>> Hi All,
>>
>> I am upgrading from 7.X to 9i Rel. 2.
>> Should I use the new feature of automatic undo management or keep on using
>> rollback segments?
>> Is the new feature reliable?
>>
>> Thanks in advanced.
>>
>> Regards,
>> Timmy Sin
>
>Go with UNDO.
>
>I have experience no problems with 9.2. And not heard of anyone that has.
>
>Daniel Morgan
>

There are some rare scenarios where AUM can be painful. IHAC who starts up the database and then hits a transaction throughput of 16,000 TPS within 8 minutes of starting the database. The system simply gets clogged trying to add sufficient undo segments, since we don't keep a memory of how many there were when the database was last shutdown. Of course, we start the database with 10 undo segments and then allocated more as needed. With this extremely unusual client configuration, AUM was killing the performance until we had created enough undo segments, so we swapped them back to rollback segments where we had preallocated sufficient numbers.

Obviously, a very unusual case. Most clients I've dealt with work fine with AUM. HTH. Additions and corrections welcome.

Pete

SELECT standard_disclaimer, witty_remark FROM company_requirements; Received on Thu Dec 19 2002 - 12:47:45 CST

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