RE: Who Write Undo Information From The DbCache To The Physically UndoDatafile.

 The DBA Administration manual has an entire chapter on managing UNDO and the Concepts manual introduces the Oracle Read Consistency model. Read these.

Then you will see that rollback segment or undo segment blocks are data blocks just like any other data blocks and get read into and written from the buffer cache.

HTH -- Mark D Powell --

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Sheldon Quinny Sent: Thursday, May 12, 2005 5:38 AM
Subject: Who Write Undo Information From The DbCache To The Physically UndoDatafile.

Hi,
I Got An Question , Been Searching The Documentation .. Not Getting An Hang Of It.=20
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I Would Like To Know , If Undo Block Is Brought In The Buffer Cache, During An Update.. SO What Process Write The Undo Block [Old Image] To The Physically Undo Datafile.=20
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And The Storage Way To Save Information On The Undo Datafile Is Diffrent >From Normal Datafile..=20
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I Would Like Some One To Help Me Explain .. Who Writes The Undo Image And How Is The Flow Work On From Buffer Cache To Undo Datafile.=20
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Can U Give Me Autentication Of This In The Oracle 9i Documentation.=20
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My Basic Logic Say So , DBWR Does The Writting Of The Data From The=20 Cache To The Datafile. And UnDo Is Also An Datafile...But A Senior Dba=20 Says Its The Server Process That Does The Writes In The Undo Datafile.=20
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Its An Senior Dba Word..So I Am Wondering. How Can I Give An=20 Explanation Of Dbwr Doing Writing ..And Not Server Process.=20
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<http://groups-beta.google.com/group/comp.databases.oracle.server/browse _thread/thread/b086f1f5cb8848a4/d0ead446037ee5a8?hl=3Den#>

 Thank You ,=20
 Sheldon Quinny

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