Re: Reorganizing tables

Dennis,

Table reorgs can be useful when there is block level fragmentation, and you
do a lot of FTS. eg. you have a table with 1000 blocks and all the data will actually
fit in 500 blocks.

It can also be useful for tables that change infrequently and are normally always
sorted on the same keys. You can load them in sorted order, though at the moment I
can't seem to recall how to do that.

Probably other reasons as well.

That said, I almost never do it myself, as I don't seem to have any problems that
warrant it.

Our previous SAP BASIS admin was *real* big on reorgs, though she wanted to do a whole tablespace at a time. I talked her out of it, or at least, she sensed
that I wasn't very cooperative on that subject. :)

Jared

DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM> Sent by: root_at_fatcity.com
 03/24/2003 09:38 AM
 Please respond to ORACLE-L  

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
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        Subject:        Reorganizing tables

We have a new manager, and at his last employer the DBAs reorganize Oracle tables on a regular basis. I don't reorg tables on a regular basis. He is lobbying us to investigate this and test whether it would or wouldn't increase performance. We are on Oracle 8.1.6, Compaq Tru64, all tables are LMT with uniform extents. This is an OLTP system, but the users continue to
add reports and the reports do quite a few full table scans. The reports are
probably the critical performance issue at this time.

• Do you do regular table reorgs? What benefit does that give you?
• Are there any indicators of when a table reorg would be beneficial?
• What sort of test would verify whether a table reorg changed performance?

Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

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