Re: Undo space

Ah yes, but they're now automatically managed for you!

Undo segments is the term used in 9i for automatically managed rollback segments. Management of the undo segments is handled internally by Oracle and all you need to do is specify the tablespace name. The tablespace is created with the CREATE UNDO TABLESPACE command after the database is created or with the UNDO TABLESPACE clause for the CREATE DATABASE command.

The thing I find really cool about undo segments is dynamic extents transfer. This allows Oracle to fill an undo segment and then (instead of adding another extent to the undo segment) to "steal" an existing free extent from another undo segment. This is only possible using undo segments, rather than rollback segments.

It's all part of one of the major pushes of 9i - make the database simpler to manage. You can still use the old manual way of doing things if you want (create the rollback segments yourself, include the ROLLBACK_SEGMENTS parameter in the initialization parameter file and so on - this is, by the way, the default still), or you can get rid of one of the things you used to have to worry about and use undo segments instead. I know which way I'm going!

--
HTH.  Additions and corrections welcome.

Pete
Author of "Oracle8i: Architecture and Administration Exam Cram"
Now got a life back again that the book is released!

"Controlling developers is like herding cats."
Kevin Loney, Oracle DBA Handbook

"Oh no, it's not.  It's much harder than that!"
Bruce Pihlamae, long-term Oracle DBA

"Mark D Powell" <mark.powell_at_eds.com> wrote in message
news:178d2795.0108130504.43059585_at_posting.google.com...


> "Keith Boulton" <kboulton_at_ntlunspam-world.com> wrote in message

news:<9Iyd7.21530$zs.184085_at_news11-gui.server.ntli.net>...


> > Just reading the Oracle 9i documentation on undo space management.

Anyone


> > else remember the before image journal?

>

> Sounds like rollback segments to me.

>

> -- Mark D Powell --