Re: Locally Managed vs Dictionary managed tablespaces

Howard J. Rogers wrote:
>
> Really?!
>
> Since its the extent allocation and de-allocation issues that they are
> particularly good at, and since rbs's are forever acquiring and dropping
> extents (or are at risk of the same), TEMP and RBS is where I recommend them
> the most.
>
> Hate to think I've dropped people in it as a result -got any specific bugs
> in mind?
>
> Regards
> HJR
> --
>
> Oracle Resources : http://www.geocities.com/howardjr2000
> ========================================
>
> "Connor McDonald" <connor_mcdonald_at_yahoo.com> wrote in message
> news:3BE19C41.283_at_yahoo.com...
> > Niall Litchfield wrote:
> > >
> > > "Howard J. Rogers" <howardjr_at_www.com> wrote in message
> > > news:3be0fd1c$0$9820$afc38c87_at_news.optusnet.com.au...
> > > > I have to say that Steve's answer where he says "I would have a
> preference
> > > > for dictionary management for any tablespace with a large number of
> mostly
> > > > small constant sized segments" rather begs the question -how do you
> ensure
> > > > that the segments *are* 'constantly sized'? Well, using locally
> managed
> > > > tablespace is the only solution that actually guarantees that!
> > >
> > > My reading of Steves answer was that he had a preference for dictionary
> > > management where the segments were lookup tables and their ilk. i.e they
> > > don't grow *by design*. This of course means , as so often, one has to
> > > actually understand the data you are looking after. In this situation I
> can
> > > go along with the recommendation - though whether I'd actually be
> bothered
> > > in practice is a moot point. LMT's are great because they avoid
> > > fragmentation caused by different sized extents. If your table isn't
> growing
> > > it won't fragment. In addition I suspect that most such tables should be
> > > allocated to a keep buffer pool anyway so physical io wouldn't be a big
> > > issue. However having said all that Steve then gives SYSTEM as an
> example of
> > > such a tablespace and it doesn't fit my reading of the above at all. Of
> > > course the best reason of all for making SYSTEM dictionary managed is
> that
> > > you have to!
> > >
> > > --
> > > Niall Litchfield
> > > Oracle DBA
> > > Audit Commission Uk
> >
> > There is still a reasonable argument for making rollback tspaces
> > dictionary based - only because of some existing bugs in most of the
> > 8.1.x releases. Other than that, I think lmt's are the canine's
> > testicles.
> >
> > Cheers
> > Connor
> > --
> > ==============================
> > Connor McDonald
> >
> > http://www.oracledba.co.uk
> >
> > "Some days you're the pigeon, some days you're the statue..."

Bug: 1176609
Bug: 1708055
Note: 112479.1
Note: 124392.1

None of which are too nasty, but with 112479.1 there are rumours that if you drop the dictionary rb seg once you've created the locally managed ones, then its feasible to get into grief during a database recovery - a hypothesis I have not tested.

(But I'm in the same boat - I've bunged in lmt's inc. rollback and temp in a number of places...)

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."