Re: optimal size for rollback

"Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message news:3D8F5F83.7DBD_at_yahoo.com...
> There are some other nice things about smu that simply can't be done
> trivially in old-style rollback. Adding/removing segs on the fly, but
> more significantly, extent stealing, ie one segment to another 'ah,
> you've finished with that extent, I'll nab it'.

This is one of the things that I'm fully prepared to say 'nope don't see how it does that' or more accurately 'Can I be absolutely sure that oracle will never reallocate an extent elsewhere when it shouldn't'. If I can then maybe I'll go with it but its all a bit hocus-pocus to me at the mo.
>
> My only criticism is basically along the lines of optimal - you don't
> control *when* the shrink occurs. But...this is *not* to say that
> shrinking rollback segs is bad - I just like to do it manually at quiet
> times.

Absolutely thats the only valid criticism of optimal in my book. It can be a bit of a killer criticism though.
>
> The reason I'm a fan of shrinks (ie as small a rollback seg as possible)
> as the smaller it is, the higher the chance it will be not be
> responsible for IO. Less IO = more performance. The risk of this is of
> course ora-1555, but less face it, if you're code catches -1555, all it
> need do is close/reopen the cursor.

!

--
Niall Litchfield
Oracle DBA
Audit Commission UK
*****************************************
Please include version and platform
and SQL where applicable
It makes life easier and increases the
likelihood of a good answer
******************************************