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Re: Convert DM TSP to LM TSP w/ lots of data

From: Tom Pall <>
Date: Mon, 28 Oct 2002 22:33:35 -0800
Message-ID: <>

I tried having Oracle convert DMT to LMT out a few times on 10 GB tablespaces. Whether or not that's a lot of data depends on you. Worked like a champ. And this was in the early days of LMT. People who pay a lot of attention to the internals will warn you that converting a DMT to LMT is not optimal. Your bitmaps wind up at the end of the files instead of the headers.

I've read posts here and elsewhere where people worried about the same issues as they did with DMT. They wanted to limit the number of extents segments grew to by creating tablespaces with different sized fixed extents. A DBA I worked with pointed out how very easy and quickly things worked with letting Oracle automatically size the next extent. I've gone that way whenever possible and have never regretted it. I've not done a rigorous benchmark but can tell you from casual observation dropping an object with lots of extents doesn't happen in the blink of an eye but doesn't lock out all other space allocation as UET/FET weren't constantly in use and the ST enque wasn't locked for exclusive use.

It's prudent to follow Oracle's recommendations if conditions permit. Create a new LMT and move your data to it.

  I am reposting this. Has anyone tried to convert a dictionary managed table space containing lots of data to locally managed? We have tried this out successfully on empty table spaces or created a new LMT tablespace and moved the existing objects to it.



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Author: Tom Pall

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