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Re: Locally Managed vs Dictionary managed tablespaces

From: Connor McDonald <connor_mcdonald_at_yahoo.com>
Date: Thu, 01 Nov 2001 19:02:25 +0000
Message-ID: <3BE19C41.283@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..."
Received on Thu Nov 01 2001 - 13:02:25 CST

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