Oracle-L: RE: Which method is more efficient

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Wed, 28 May 2003 08:59:51 -0800
Message-ID: <F001.005A46AE.20030528085951@fatcity.com>

Bryan - If this is a critical issue, I would try it both ways on a test database and use log miner to examine the amount of redo that is generated. My recollection is that you will find that the redo record records the before and after data for each field. So just updating all fields may generate significantly more redo. But don't trust my recollection on this issue, test it yourself.

Dennis Williams
DBA, 80%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Wednesday, May 28, 2003 10:50 AM
To: Multiple recipients of list ORACLE-L

Hello everyone,

I have a question for the group of which method is more efficient.

To set the stage my company has a process to load part changes from vendors into the tables in an 8.1.7.4 Oracle database with archiving on and this database has a standby database at disaster recovery site, so nologging is not an option.

There is a discussion going on as to which method is more effective for updating the information in a table. In looking at effectiveness, I am looking at reducing the amount of redo information produced and having the database do the least amount of work.

Method 1 is to update the information only for the fields that have changed, 1 field at a time.
Method 2 is to update the information for all the fields in the record whether they have changed or not, 1 record at a time.

The size of the record is 1843 bytes and the distribution of field sizes: 2 fields varchar2(240).
1 field varchar2(150)
15 fields varchar2(50)
1 field varchar2(3)

2 fields varchar2(20)
4 fields varchar2(40)
3 fields varchar2(1)
2 fields varchar2(25)

2 fields number(10,2)
1 field number(13,2)
1 field number(1)
1 field number
1 field varchar2(6)
1 field number (17,2)
1 field varchar2(4)
3 fields that are date.

In the past couple of months the average number of fields changed per record was 3 to 4 fields per record.

Thanks for your help,

Bryan Rodrigues
Oracle DBA
Elcom, Inc.

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Author: Rodrigues, Bryan
INET: BRodrigues_at_elcom.com

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Author: DENNIS WILLIAMS
INET: DWILLIAMS_at_LIFETOUCH.COM

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