Re: rollback segment question

Hi Daniel, Stef and all,

In person, I usually repeat a question back to make sure I understood it correctly. I guess it's a little harder in this environment :(

I interpreted the question as "is it possible to "assign" the segment to a specific data tablespace" where the word assign means any changes made to objects residing in the tablespace are recorded in the assigned rollback segment. It's a question I've been asked before. The answer to which was my ramblings

If the intent of the question was "is it possible to "create" the segment to a
specific data tablespace" then absolutely, disregard my ramblings, and yes rollback segments, like all other segments, can only be created in the one tablespace. In fact it's common practice to put such rollback segments in the one, appropriately striped tablespace.

Thanks for the clarification and sorry for any confusion.

Cheers

Richard

Daniel Morgan wrote:
>
> Richard Foote wrote:
>
> > Hi Stef,
> >
> > One thing to add.
> >
> > With the way rollback (undo) is automatically handled in 9i (providing
> > you don't get ORA600s), the sharing algorithm is improved in that RBS
> > can "steal" extents from each other. This means the SET TRANSACTION
> > statement is now redundant (and could cause errors unless appropriate
> > parameters are set).
> >
> > Cheers
> >
> > Rihcard
> >
> > Richard Foote wrote:
> > >
> > > Hi Stef,
> > >
> > > The short answer is no.
> > >
> > > The reason being that Oracle's way is better :)
> > >
> > > By allowing all rollback segments to be shared and used in a round robin
> > > fashion, this means all things being equal, that the load among the
> > > rollback segments be evenly spread. This is a desirable outcome.
> > >
> > > By "hard coding" which rollback segment belongs to which tablespace, or
> > > which table or which user, etc., you're increasing the likelihood of a
> > > particular RBS being overloaded while others are sitting back and
> > > relaxing.
> > >
> > > An option you do have if you really want to use a particular RBS at the
> > > transaction level, is to use the SET TRANSACTION USE ROLLBACK SEGMENT
> > > blah. This is typically done when the transaction is large and the blah
> > > RBS is a specially large sized one that can cope with the excess amount
> > > of data. This though is an exception and one that is quite commonly
> > > abused.
> > >
> > > Cheers
> > >
> > > Richard
> > >
> > > stef wrote:
> > > >
> > > > Hi, everybody
> > > >
> > > > I'm a newbie in Oracle :) and I would like to know one thing
> > > >
> > > > When you create a rollback segment, is it possible to "assign" the segment
> > > > to a specific
> > > > data tablespace..? like Sybase or sql server do.
> > > >
> > > > example:
> > > > In the same database "TEST_DB" :
> > > > 1) create a data tablespace "datas_01".
> > > > 2) create a second data tablespace "datas_02".
> > > > 3) then create a rbs called "global_rbs" (mapping on a tablespace YYYY, not
> > > > important )
> > > >
> > > > Now, as I can see, all datas_01 and datas_02 will "use" the same global_rbs
> > > > ok...
> > > > Can I say now, datas_01 use only global_rbs and datas_02 use... another rbs
> > > > for example ?
> > > >
> > > > thanx....
>
> Actually, Richard, you are incorrect. But not because you don't know the correct
> answer but because I think you are addressing a question that was not asked. The
> original question was:
>
> "When you create a rollback segment, is it possible to "assign" the segment to a
> specific data tablespace..? like Sybase or sql server do."
>
> In Oracle all rollback segments are assigned to, or created in, a specific
> tablespace. There is no other way to do it.
>
> The question I think you answered was whether a rollback segment could be assigned
> to a specific user or schema ... and to that the answer is, in fact, no.
>
> Daniel Morgan