Re: supplemental logging questions and golden gate

  • From: Alex Fatkulin <afatkulin@xxxxxxxxx>
  • To: oracledbaquestions@xxxxxxxxx
  • Date: Fri, 22 Jul 2011 10:30:35 -0400

By default Oracle logs only columns that changed. The whole purpose of
supplemental logging is to enable logging for something that didn't.

If you execute

update emp set name='Bob' where emp_id=100

you won't get emp_id logged in the redo because it did not change
unless you enable supplemental logging for emp_id column (which is
required on the receiving end of the replication to resolve the row
being updated). The whole before/after image point, when applied to
supplemental logged columns, is a bit moot since the column value did
not change. The "before image" term in the doc might be a bit
confusing until you realize that.

On Fri, Jul 22, 2011 at 10:08 AM, Dba DBA <oracledbaquestions@xxxxxxxxx> wrote:
> I am confused. I thought supplemental logging only needs to log the before
> image of every column, if you do not log based on a unique or primary key?
> If you do, it only gets the before image of the column that changed.
> However, that before image should already be logged to redo, since that
> image is copied to the undo tablespace and that generates redo.
>
-- 
Alex Fatkulin,
http://afatkulin.blogspot.com
http://www.linkedin.com/in/alexfatkulin
--
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