Re: Rollback segments - Is it better to have 2 or 10 extents

> The reason why 2 extents is bad is that a transaction
> that starts in one extent and crosses into the second
> extent makes the entire rollback segment unavailable
> for any other transaction to start. (True up to 7.3, but
> I haven't checked it for 8.0, 8.1).

That's not true. Oracle will create additional extents for the RBS until you reach the MAXEXTENTS parameter for the RBS.

But dynamic expansion takes time and causes disk activities and consumes cpu. You do not want it to happen while a user is trying to do updates from performance perspective.

>
> 10 is better because this denial of access still leaves
> 8 extents for other transactions to start in.
> --

Create only enough extents for all your concurrent activities. More RBS with less extents are usually better than less RBS with large number of extents.
But different systems have different tuning requirements.

Dowson

>
> Jonathan Lewis
> Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk
>
> ragu sekar wrote in message <380b465e_at_www2.iaol.com>...
> >
> >Hi
> >
> >I read somewhere that it is better to have 10 extents for a rollback
> segment than just 2 extents? Pl comnfirm or contrast this/ Thanks
> >
> >ragu
Received on Wed Oct 20 1999 - 21:02:33 CDT