Re: Urgent!!!!Rollback segment problem

hi mike

a transaction uses extents of a rollback segment in an ordered circular fashion and
a transaction can reuse an extent within a rollback segment ONLY if it is free or inactive.
so if your first transaction uses 50mb of your single extent and the next 70mb transaction starts,
you 're running in trouble with your last 20mb of the second transaction, because oracle can't
reuse this already used extent.

BUT, why will you use only one extent. i can not see any reason to do it this way

thomas

Mike Ng schrieb:

> Hi all,
>
> I have asked the following question before, and Mr. Anjum have answered me.
> But now I have another question.
> Assume I have four rollback segment and each have one 100 meg extent.
>
> initial 102400 k, next 0 k, minextent 1, maxextent 1
>
> Assume that no one transaction will use more than 100 Meg, and one
> transaction must finish before another transaction will use to exceed 100
> meg. Now, two transactions run in the same rollback segemt. One use 50 meg
> size and another use 70 meg size in rollback segment. Assume that first
> transaction finish the job before the second transaction will use the size
> exceed 100 meg. I have a question here that
>
> Can the second transaction use the rollback segment which was freed by first
> transaction in the SAME extent?
>
> I have the above question since I see all example that the space freed is
> based on extent scale, not block scale. So I doubt the second transaction
> cannot reuse the space freed by first transaction.
>
> If the above case is workable, the performance should be the best. Right or
> wrong?
>
> Thanks to answer my stupid question in advanced.
>
> Best Regards,
> Mike Ng
>
> In article <38b1fdc0_3_at_news1.prserv.net>,
> "Mike Ng" <mike_at_email.tech-trans.com> wrote:
> > Hi all,
> >
> > I hava a question that
> > Can I allocate a very large extent for each rollback segment? Multiple
> > transactions can use the same extent in rollback segment. Is it right?
> Or
> > one new transaction need at least one new extent in rollback segment.
> > It makes me mess.
> >
> > Thanks in advanced.
> >
> > Best regards,
> > Mike Ng
> >
> >
Received on Tue Feb 22 2000 - 07:28:42 CST