Re: Understanding Rollback Segment Sizes

Brian Peasland wrote:
> > I appreciate the input you provided. Unfortunately it didn't really
> > help answer the questions I asked. Don't get me wrong, I will certainly
> > review all the points you made. It's just that I was hoping to get a
> > better idea in "layman's terms" whether I had too much or too little
> > space and how to properly calculate it.
>
> Then in "layman's terms", start using UNDO tablespaces and you won't
> have to worry about sizing the rollback segments. Oracle will handle
> this for you. It doesn't get any easier than that. First, create the
> undo tablespace:
>
> CREATE UNDO TABLESPACE undotbs DATAFILE '/dir/undotbs01.dbf'
> SIZE 1000M AUTOEXTEND ON NEXT 1000M MAXSIZE 10000M;
>
> Then set up the database to use the UNDO tbs by modifying the following
> initialization parameters:
>
> UNDO_MANAGEMENT = AUTO
> UNDO_TABLESPACE = undotbs
> UNDO_RETENTION = 900
>
> Bounce the instance and you're off and running.
>
> Cheers,
> Brian

Thx Guys for all the input. I reviewed the Concepts manual again this morning, exactly as I understood it, then reviewed the "Whats new for 9i" regarding Undo Tablespaces, and finally reviewed the Admin guide for the Undo tablespace and the difference between AUTO and MANUAL manging of undo space. (essentially using RBS vs UNDO).

As Brian indicated, the "set it and forget it" aspect of Undo tablespaces looks like the way to go. Now the only issue is convincing my management that we should do it that way instead of the way our five other Oracle sites are configured, and to see if our application developers can give me any info on whether our software ever explicitly tries to access a rollback segment, such as for month-end processing or cleanup utilities. Received on Thu Jan 18 2007 - 09:57:58 CST