Joel Garry wrote:
> "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message news:<PTlX9.29896$jM5.77257_at_newsfeeds.bigpond.com>...
> > "Joel Garry" <joel-garry_at_home.com> wrote in message
> > news:91884734.0301211649.2d029eda_at_posting.google.com...
> > > "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> > news:<IegX9.29683$jM5.76837_at_newsfeeds.bigpond.com>...
> > > > "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message
> > > > news:b0jcjl$igp$1$830fa78d_at_news.demon.co.uk...
> > > > > Diskspace may be cheap, but I/Os are not, and
> > > > > any strategy that results in redundant I/O is inherently
> > > > > suspect. Allowing undo segments to become
> > > > > unnecessarily large is one way of generating
> > > > > redundant I/O.
> > > > >
> > > >
> > > > But since SMON shrinks anything that it considers too large every 12
> > hours
> > > > or so, this isn't going to be an issue, is it?
> > >
> > > Sounds like the real world is bound to undo all gains from moving to
> > > LMT's by simply requiring too much undo for useless flashbacks.
> > >
> >
> > Too much undo is simply a question of storage. At this stage, unless
> > Jonathan cares to clarify. Quite what benefits of LMTs that mitigates, I
> > can't see. LMTs eliminate possible contention on UET$/FET$ data dictionary
> > tables when allocating or deallocating space; they eliminate the possibility
> > of tablespace fragmentation; they make segment sizing decisions a
> > no-brainer. Now what has an 'excess' of undo to do with any of that?
>
> Consider a humongous DW combined with a humongous transactional labor
> and inventory system with humongous RBS's and product planners running
> humongous part and labor allocation what-if scenarios for building
> jumbo-jets on it. For each what-if, when they are done, they
> flashback. At some point, they are doing so much undo I/O, it becomes
> substantially like the old contention problems.
>
> jg
> --
> @home is bogus.
> Control-Alt-Delete helps keep your password safe.
> Unless you happen to have a new multipartite boot sector virus.
I'm not sure I understand why you would flashback on a DW. A DW should not be a transactional system.
Daniel Morgan
Received on Mon Jan 20 2003 - 20:29:33 CST
