Re: Difference between Redo Log Buffer & Rollback Segment?

> Could anyone tell me what the difference is between them?

It might help to think of rollback as "Undo". Rollback remembers all the changes made to a database during a transaction. If the transaction fails or if you decide it wasn't what you wanted to do, you (or Oracle itself) can "Undo" the changes and revert to the original data in the database.

Redo, as it's name suggests, allows Oracle to roll forward and re-apply changes that may have been lost, for instance in the event of a database crash. When the instance starts up, Oracle checks the "age" of the data files against the control file and, if it finds a datafile is out of date, applies the redo (if available!) to bring it in line with the control file. If necessary it can then roll back any transactions which were incomplete at the time of the crash.

I'm sure you'll get lots more technical explanations, but that's the gist of it. Have a look at the Server Administrators Guide more information.

Robin   Received on Wed Aug 12 1998 - 03:06:09 CDT