RE: redo logs

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Sat, 17 May 2003 20:11:39 -0800
Message-ID: <F001.0059BFB4.20030517201139@fatcity.com>

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: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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