Re: to undo or not to undo
- From: Daniel Fink <Daniel.Fink@xxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 25 Feb 2004 09:37:59 -0700
Howdy Barb!
I would create the undo tablespace, shutdown (in consistent mode),
perform a full backup, change the parameters, restart the db, drop
the rbs tablespace. Make sure you shutdown in consistent mode or
else you can trash the database. Based on your undo_retention
setting, I'd start out with an undo tablespace that is at least 3x
the size of the current rbs tablespace. Closely monitor v$undostat
using Kirti's methods and resize as needed.
One area to be careful about is dealing with a high throughput/high
concurrent transaction system. There seem to be problems with
housekeeping that has been identified by at least 3 credible
sources.
You also need to purchase the guaranteed Automatic Undo Management
tool that I unveiled at my RMOUG presentation. While the
British-specific version is the best, there are suitable versions
available in the states.
Dan
Barbara Baker wrote:
> Howdy, list.
> For those of you who migrated a database from 8i to
> 9i, did you move convert to undo tablespace
> immediately? Did you run for awhile still using
> rollback segments then convert later? Any gotcha's?
>
> I cannot find a concise doc on how to change over.
> (I'm using notes from Kirti's excellent RMOUG
> presentation on "Understanding Automatic Undo.." but
> I've already forgotten stuff.)
>
> Here are the steps I know. What I do not know is when
> to remove my rollback segments. If I add the undo
> params to init then bounce the db, can I then offline
> the rbs segs and tablespace after I come back up? Or
> do I offline them before I bounce the db?
>
> Anyone know of a doc that outlines this stuff?
> Thanks for any help.
> Solaris 9 Oracle 9.2.0.4
> Barb
>
> (here's what I think I need to do)
>
> Changing Rollback Segments to Undo
>
> set compatible 9.0.0 in init (currently 8.1.7.4)
>
> create undo tablespace
> create undo tablespace undotbs1
> datafile '/class17db/u01/undotbs1.dbf'
> size 500m;
>
> insert init parameters
> undo_management=AUTO
> undo_retention=10800
> undo_tablespace=UNDOTBS1
> undo_suppress_errors=TRUE
>
> shut down and restart database
>
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