Re: LMT and DMT

"Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in message news:3e3f9640$0$232$ed9e5944_at_reading.news.pipex.net...
> "tingl" <one4all_at_all4one.not> wrote in message
> news:tUE%9.6058$6P2.678346_at_newsread1.prod.itd.earthlink.net...
> > Hi Richard,
> >
> > I am not sure what you meant by too simplistic. My intention was to make
> it
> > less simplistic
> > than just "LMT is better.". Anyway there is a tradeoff between ease of
> > maintenance and
> > flexibility. LMT and DMT each has pros and cons. Neither is better than
> the
> > other in all
> > situations.
>
> If you accept that
>
> 1) LMTs enforce standard storage conditions and so prevent fragmentation
> 2) LMTs reduce (sometimes drastically) IO and locking due to eliminating
> transactions against UET$ and FET$.
> 3) LMTs do not suffer even with large numbers of extents.
>
> I find it difficult to envisage any circumstance when a DMT would be
> preferred. I have seen people object to all of the above (though rarely
2).
>
>
> --
> Niall Litchfield
> Oracle DBA
> Audit Commission UK
>
>
>

I would object 1, partially accept 2, and totally accept 3.

1. To completely eliminate fragmentation, you can also make all extents the same size in DMT, even though fragmentation is more of an issue in theory than in practice.
2. The effect of this would depend on how well or poor the DMTs are configured.
3. This is where LMT shines but fewer extents is still better.

Wouldn't it be nice to use bitmap and at the same time having less restriction on extent sizes in
the same tablespace. Received on Tue Feb 04 2003 - 18:53:40 CST