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RE: Storage guidelines in 9iR1 ??

From: Wolfgang Breitling <>
Date: Wed, 26 Mar 2003 14:43:49 -0800
Message-ID: <>

Since I am using LMTs exclusively (so far only in 8.1.7) I was curious and did some tests on a system on Linux. I didn't find a particular slowdown during load using sqlldr and my data doesn't show a performance degradation at ~1024 extents for the sql (count(0), sum where, and sum group by, all by fts). In my case it happens somewhere beyond 3000 extents. The cpu time for full scans stayed linear through the entire range (128 up to 6400 extents); the elapsed times initially stayed very close to the cpu time, but beyond 3000 (3072?) grew quickly to 2-3 times cpu time.

I haven't done any comparison to DMT.

At 11:10 AM 3/21/2003 -0800, you wrote:
>You're correct. I should have quantified what I meant by significant. As
>well as given more detail on what I was doing. That said, here is what I
>remember of what I was doing....
>Specifically, At the request of management, I was testing the performance
>and extent allocation of locally managed tablespaces v.s. dictionary
>tablespaces. I was to give a summary of my results and a recommendation as
>to how new tablespaces were to be created.
>That said, I create 2 tablespaces. One dictionary managed and one locally
>managed (uniform extent size) on the same instance, same logical volume on
>the disk array and same extent sizes (1mb)
>The same table was created in both tablespaces, using the default storage
>I used SQL Loader to load the same data into both tables tablespaces
>multiple times. The source file was about 1mb.
>I was mostly testing non-direct path insert performance (via sqlldr) and
>select performance via several scripts (using sqlplus).
>What I found was that the performance of sqlldr stayed remarkably steady
>the dictionary-managed tablespace well past 2000 extents. The sqlldr
>run-times increased by about 5-10% for the locally-managed after about 1024
>extents had been reached.
>The performance of the select statements degraded in a linear fashion,
>on the number of rows. The exception was that the LMT table saw a 5-10%
>degradation in performance after about 1024 extents were reached.
>No updates or deletes were performed on the tables. Also, there were no
>indexes or constraints on the tables. Nor did I generate statistics.
>And this was repeatable as I dropped and recreated the tablespaces several
>The methodology was as follows, recording the timing at each step
>1) Load the file one time into each of the tables
>2) note the number of extents
>3) perform the selects
> -- count(*)
> -- select * from xxx where id = 1;
> -- a select with a group by.

Wolfgang Breitling
Centrex Consulting Corporation

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Author: Wolfgang Breitling

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Received on Wed Mar 26 2003 - 16:43:49 CST

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