Re: Difference between Redo Log Buffer & Rollback Segment?

The redo logs are used to redo or do over things that have been entered into the database, and the rollback segments are used to undo things that have been 'entered' into the database.

lets say you have a transaction that affects 1 million rows, all of the changes will be stored as both redo and undo. Now lets say that you type commit, now everything in the log buffer will be written to your online redo log files and your rollback segments will no longer hold the extents that held this transaction. Now you have a disk failure.
you will apply the redo to redo (do over) that transaction.

Next example:
same transaction, but right before you type commit there is a power surge and your session just dies or you type rollback. NOW all the changes that you made (before commiting) will be rolled back and undone. I hope this helps.
and I think I'm right...

Glen Upreti
glen.upreti_at_nau.edu

Violin wrote:
>
> I'm a little confused about them.
> Could anyone tell me what the difference is between them?
> Thank you so much.... :)
> Please Cc to : violin.hsiao_at_mail.pouchen.com.tw
Received on Fri Aug 21 1998 - 10:03:54 CDT