Re: OPTIMAL on Roll Back Segments

On Wed, 14 Jul 2004 13:14:11 -0400, "paddy_nyr" <mpprpp_at_yahoo.com> wrote:

>I'm using Oracle 8.1.7.4 on Solaris 8 and I'm getting a number of "snapshot
>too old" errors when I run my production process.
>
>I read that you should increase the number of rollbacks segments and so I
>did from 100 to 200, but still get the "snapshot too old"
>
>My initital storage is 5m, minextens 4, maxextents249, next 5m, optimal 20m.
>
>I read somewhere that not specifying an OPTIMAL size when creating your
>rollback segments helps because, if set, Oracle will dynamically shrink
>rollback segments which have grown larger than the specified size by
>deallocating extents. However, it may deallocate extents which still contain
>committed pre-images required for read-consistency. Not setting the OPTIMAL
>value eliminates this cause of "snapshot too old".
>
>
>Is this true?
>
>
>Thanks

setting OPTIMAL is a recipe for getting ora-1555

>
>

--
Sybrand Bakker, Senior Oracle DBA