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Hi Daniel,
I think the answer to your question is the very big danger to performance for the great many who would abuse such an option.
Currently, Oracle does a pretty good job of automatically spreading the load across the available rollback segments (even better so in 9i). Potential issues with specifying a RBS for a user includes:
When I close my eyes and imagine all the issues that can arise if RBSs were assigned to individual users, it's not a pretty sight. The fact that Oracle spreads undo load per transaction is actually a very clever and efficient way to manage things. The fact that undo segments now can interact and "borrow" storage from each other is very nice (when it works :(.
The option to set a transaction to use a specific RBS was the way to have some control over this (which is now of course unnecessary in 9i (when it works :( again.
I for one would really question such a user option that assigned an RBS to a user. It would cause many more issues than it solved.
Then again, I could be wrong :)
Richard
"Daniel Morgan" <dmorgan_at_exesolutions.com> wrote in message
news:3D41797B.8E889314_at_exesolutions.com...
> Pete Sharman wrote:
>
> > In article <ahrlbh$vi73t$1_at_ID-82797.news.dfncis.de>, "Steven" says...
> > >
> > >Hi,
> > >
> > >I'm wondering if it is possible to set a specific rollback segment for
a
> > >user so that user only uses the specified rollback segment. My problem
is
> > >that sometimes I perform large transactions and want to use the large
> > >rollback segment. However, I cannot specify the rollback segment using
"set
> > >transaction......" because I am accessing the data through an
application.
> > >
> > >Any help will be appreciated,
> > >Regards,
> > >Steve.
> > >
> > >
> > >
> > Nope, Niall's approach is the only way that this will work. Even then,
you're
> > not guaranteed that other users won't use the same rollback segment.
> >
> > HTH. Additions and corrections welcome.
> >
> > Pete
> >
> > SELECT standard_disclaimer, witty_remark FROM company_requirements;
>
> Which leads to the obvious question. Why hasn't Oracle implemented private
> rollback segments? I can assign a user a default tablespace, a temp
tablespace,
> why not user-specific rollback? It seems to me it would be a technical
no-brainer.
>
> CREATE USER xyz
> IDENTIFIED BY xyz
> DEFAULT TABLESPACE abc
> TEMPORARY TABLESPACE def
> ROLLBACK SEGMENT ghi
> QUOTA ... ON
>
> It would just be one more way for DBAs to control resource utilization and
I/O.
>
> Daniel Morgan
>
Received on Sat Jul 27 2002 - 20:10:02 CDT