Table-Extents / Performance
Date: 11 Sep 2001 02:52:03 -0700
Message-ID: <b2677297.0109110152.64cd8786_at_posting.google.com>
Hallo !
Recently I read in a paper that it's no problem to have tables with
many extents in a database
(http://technet.oracle.com/deploy/availability/pdf/defrag.pdf). My
DBA-Handbook says, it is the best to put the whole table into one
extent.
I'm working on a database with no online-transactions - only
batch-jobs (inserts and deletes, very few updates). Last week I had to
remove the data from some tables. I did that by "delete from table
xxxx". It was a hard job, because it took very very long.
Afterwords I looked at some tables with the schema-browser of toad.
Although the tables where empty it took very long (maybe 20 seconds)
for toad to show the table-data-view. The tables had some extents
(maybe 10 - 30).
After I had done a "truncate table xxx drop storage" the access-speed
to these tables was "normal" again (1 - 2 seconds).
I think this is because the tables had only one extent left after the
truncate statement.
So why can anybody say that the number of extents is not important for
performance ?
Any Ideas ????
Marcus Received on Tue Sep 11 2001 - 11:52:03 CEST