Re: Redo log and rollback segment?

I think you explained in a thread a few months ago that redo actually contains both before and after images. Is that correct?

Thomas Kyte wrote:

> 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 Sun Sep 19 1999 - 01:49:33 CDT