When this check box is checked the 'Source columns' edit window is disabled. By default, and with this box unchecked, a load table uses the contents of the 'Source columns' to specify which columns are being extracted during a table load.

When this box is checked the load process builds up the statement to select from the source table(s) by looking at the two fields source table and source column and any transformations associated with each column in the load table. If a transformation is present then the transformation overrides the contents of source table/source column. See the following section for more information on transformations.