Re: question about automatic undo management

DA Morgan <damorgan_at_exesolutions.com> wrote in message news:<3E2CB08D.694B7E6A_at_exesolutions.com>...
> 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.

Sorry, I worked for quite a while at a place where the management did not quite accept that. In fact, they quite actively pursued the combination to the tune of millions of dollars. You know, "Data Architects" who think everything should be in one giant db and all that. They tried to get me into that hell, but I resisted, I was only interested in transactionals at that time. Of course, that meant dblinks into hell for some apps, but there you go. Full employment for... someone.

And I think there are a lot of places that are actively pursuing such a "strategic vision." I bet they really look forward the multisize block features, eh?

jg

--
@home is bogus.
I like a challenge, but...