RE: redo logs

Yes. Remember that Oracle doesn't wait for a commit before it writes redo. It is even possible for uncommitted data to get written to the data files. This is a real performance boost on a busy system. In case of a crash, Oracle must be able to recreate the "before" image of the data.

   If you become more interested in this, take a look at LogMiner. Once you see all the details in a redo log, you'll be much more impressed with Oracle's integrity and throughput! And a good time to practice with LogMiner is when you aren't under pressure.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Monday, May 19, 2003 4:58 PM
To: Multiple recipients of list ORACLE-L

Dennis , so what you are trying to say is that the redo logs store undo data also ?

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Sunday, May 18, 2003 09:41

> Not every statement is committed. Some are rolled back. So when the
database
> is recovered, these statements must again be rolled back.
>
> Dennis Williams
> DBA, 80%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Saturday, May 17, 2003 9:09 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Hello list
>
> the "backup and recovery concepts" manual says :"Each redo record contains
> both the old and the new values. Oracle also records the old value to an
> undo block located either in a rollback segment (if running in manual undo
> management mode) or in a dedicated undo tablespace (if running in
automatic
> undo management mode)."
>
> Does this mean that undo data is stored in both the undo tablespace and
the
> redo
> logs ?
>
> I thought that only statements were stored in the redo log file.
>
> If undo data is stored in the redo logs also, then , do we need the undo
> tablespace during recovery ? shouldn't the redo logs be enough ?
>
> --
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> Author: <bulbultyagi_at_now-india.net.in
> INET: bulbultyagi_at_now-india.net.in
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> Author: DENNIS WILLIAMS
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: <bulbultyagi_at_now-india.net.in
  INET: bulbultyagi_at_now-india.net.in

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-- 
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-- 
Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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