Re: LMT and DMT

From: Stephan Bressler <stephan.bressler_at_siemens.com>
Date: Mon, 3 Feb 2003 14:41:14 +0100
Message-ID: <b1lrf9$l4r$1@news.mch.sbs.de>

<snip>
> thing. They prevent "tablespace fragmentation" (which isn't a performance
> issue, but is definitely a waste of space issue).
Are you sure? This is true in case of uniform LMTs, not in system managed LMTs. You can mimic uniform LMTs with DMTs, too, but choosing 3 TBS (e.g. a 64k TBS for small objects, a 1M and a 8M for larger objects).

> They prevent contention
> for the data dictionary when dozens of segments all decide to extend at
the
> same time.

Ok, if you do a lot of space management or you have 10.000s of extents.

I don't like LMTs for the following reasons: - with uniform I need to know the size of the object from the beginning - with system managed LMTs I end up with fragmentation (64k, 1M, 8M extents) and a huge number of extents
- access to dba_extents is unacceptable slow when >2000 extents are allocated

Even on 9i, I used DMTs (not for undo and temp).

Stephan Received on Mon Feb 03 2003 - 07:41:14 CST