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 -- //www.freelists.org/webpage/oracle-l