Do not add columns to a key after Oracle GoldenGate starts extracting data from the table. This rule applies to a primary key, a unique key, a KEYCOLS key, or an all-column key. DB2 LUW does not supply a before image for columns that are added to a table. If any columns in a key are updated on the source, Oracle GoldenGate needs a before image to compare with the current values in the target table when it replicates the update.