Re: undo and insert

Just the previous version of the changed columns, plus an overhead of about 80 bytes which relates to ITLs, linked lists, operation descriptions etc.

Bear in mind that undo relating to indexes is not the same as undo relating to tables, though. An update to an indexed column results in one index entry being deleted (so the whole index entry is coped to the undo) and another index entry being inserted (which also means the whole (new) index entry being copied to the undo).

There is a statistic relating to undo size in v$sysstat/v$sesstat in the most recent versions of Oracle.

While a transaction is active, you can track it in v$transaction, and there are two columns in that view giving you information about the undo - used_urec (undo records created) and used_ublk (undo block used).

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

  The educated person is not the person   who can answer the questions, but the   person who can question the answers -- T. Schick Jr

One-day tutorials:
http://www.jlcomp.demon.co.uk/tutorial.html

Three-day seminar:
see http://www.jlcomp.demon.co.uk/seminar.html ____UK___November

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Wednesday, December 24, 2003 8:44 PM

> I have a related question : What about update? In rollback segment :
> Will it store the whole row for before image or just the changed column
> and rowid. Is there a way to get the size of the rollback from some
> where in the database. or v$ views. Like we can get an idea about redo
> size from redo log files generated. Thank you
>
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).