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Home -> Community -> Usenet -> c.d.o.server -> Re: Which RBS is my Update using ?
Paul Brewer wrote:
> "Daniel Morgan" <dmorgan_at_exesolutions.com> wrote in message
> news:3D8F8B35.339D051C_at_exesolutions.com...
> > Paul Brewer wrote:
> >
> > > "Daniel Morgan" <dmorgan_at_exesolutions.com> wrote in message
> > > news:3D8E4E10.8AAABEFC_at_exesolutions.com...
> > > > Paul Brewer wrote:
> > > >
> > > > > "Daniel Morgan" <dmorgan_at_exesolutions.com> wrote in message
> > > > > news:3D88D674.1619D215_at_exesolutions.com...
> > > > > > Tanel Poder wrote:
> > > > > >
> > > > > > > Hello,
> > > > > > >
> > > > > > > > What you are missing ... is that rollback segments need to be
> able
> > > to
> > > > > expand to
> > > > > > > > handle the largest transaction on the system. That is not the
> same
> > > as
> > > > > saying they
> > > > > > > > need to permanently be large enough to handle the largest
> > > transaction
> > > > > on the
> > > > > > > > system.
> > > > > > >
> > > > > > > I still don't see why rollback segments in my configuration are
> less
> > > > > > > expandable than "They should all be identical and sized to
> handle
> > > the
> > > > > > > largest transaction on the system" configuration which you
> posted
> > > > > > > yesterday..
> > > > > > >
> > > > > > > But about the cheap price of disk v.s. administration work cost,
> I
> > > agree
> > > > > > > with you.
> > > > > > >
> > > > > > > Thank you for your time,
> > > > > > > Tanel.
> > > > > >
> > > > > > I'm not sure I understand your question. Rollback segments expand.
> And
> > > > > expand until
> > > > > > they either hit the maximum allowed extents parameter or run out
> of
> > > disk
> > > > > space. So as
> > > > > > long as any rollback segment can expand enough to hold any
> transaction
> > > > > which rollback
> > > > > > segment becomes irrelevant.
> > > > > >
> > > > > > If you try to force a transaction into a specific rollback
> segment.
> > > And
> > > > > for any reason
> > > > > > that specific segment is unavailable. The transaction will fail.
> > > > > >
> > > > > > Daniel Morgan
> > > > > >
> > > > >
> > > > > OK, I'll rise to this one.
> > > > >
> > > > > Our organisation runs Peoplesoft in Atlanta.
> > > > > Each morning at 3 a.m. we replicate about 80 of the Peopleshit
> tables
> > > back
> > > > > to the U.K., then sort them out into something like a rational
> structure
> > > for
> > > > > reporting purposes.
> > > > > So, during the day, the U.K. tables are read only, and we don't need
> > > much by
> > > > > way of rollback segments. However, during the actual replication
> process
> > > we
> > > > > need to use a segment ROLL_BIG, so that the entire refresh group
> will
> > > either
> > > > > succeed or fail.
> > > > >
> > > > > Paul
> > > >
> > > > And your point is? ;-)
> > > >
> > > > All I said was make all of your rollback segments capable of expanding
> to
> > > be as
> > > > large as ROLL_BIG. The cost of doing this is zero.
> > > >
> > > > Smaller transactions won't ever expand beyond whatever transactions
> they
> > > > receive. But if they do end up being the rollback segment chosen for
> the
> > > nightly
> > > > process ... they will not fail. Right now you have a single point of
> > > failure.
> > > >
> > > > Daniel Morgan
> > > >
> > > Daniel,
> > >
> > > ROLL_BIG is offline during the day. The nightly session brings it
> online,
> > > does 'set transaction use rollback segment ROLL_BIG', does its work,
> then
> > > takes it offline again.
> > > The other rollback segments are all equally sized (and much smaller).
> > > What's wrong with that?
> > >
> > > Regards,
> > > Paul
> >
> > Nothing until the first time something goes wrong: Then everything.
> >
> > What's wrong with resizing all of your rollback segments?
> >
> > Daniel Morgan
>
>
Because it doesn't cost you more than five minutes to prevent a potential disaster. The same reason people buy health insurance when they are not sick.
And likely they don't need to be 1GB and neither does BIG_ROLL. They just need to be able to expand to that size.
Daniel Morgan Received on Tue Sep 24 2002 - 11:01:10 CDT
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