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Re: Rollbacks

From: Marc Hansen <Marc_Hansen_at_iname.com>
Date: Thu, 27 Aug 1998 15:42:34 -0600
Message-ID: <35E5D2CA.6572EB01@iname.com>


An active rollback segment holds data blocks of an active transaction

non-active rollback segment has no active transactions against it.

a chained row is a is larger then the db block could handle. IE. DB_BLOCK = 2k the row is 3K in size.

a migrated row is when a update of an exsiting row occurs with the update increasing the row size by more then what the free space in the block could handle. migrated row occur when the PCTFREE is set to small and are possilbe when columns allow nulls or are variable in size.

Both migrated and chained rows hurt the cache hits on the server.

Marc
Keane Inc.
Marcus_Hansen@iname.com

Arthur Merar wrote:

Hello,

Being fairly new to Oracle I need some help in understand this concept.
What is meant by an 'active rollback segment' verses a 'non-active
rollback segment'.

Also, what is the difference between 'chained blocks' and 'migrated
blocks'.....

Thanks for all your help,

--

"A real friend is someone who knows all about you and still respects
you."

Arthur
amerar@unsu.com
ICQ#:663601
http://www.unsu.com

 

Received on Thu Aug 27 1998 - 16:42:34 CDT

Original text of this message

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