Re: Redo log and rollback segment?

A copy of this was sent to jonathan_at_ms35.url.com.tw (Trister Yang) (if that email address didn't require changing) On 3 Sep 1999 02:10:10 GMT, you wrote:

>I always so confuse about what's different between redo log and
>rollback segment ?
>
>I will appreciate for your answer!
>
>Thanks!

REDO is 'redo' -- it can redo a transaction. It is after images of changes. It is predominantly used for RECOVERY after a crash or media failure.

ROLLBACK is 'undo' -- it can undo a transaction. It is before images of changes. It is predominantly used to rollback a transaction after an online error or to provide read consistent, nonblocking views of data.

--
See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st  

Thomas Kyte                   tkyte_at_us.oracle.com
Oracle Service Industries     Reston, VA   USA

Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Fri Sep 03 1999 - 08:05:59 CDT