Copy stage: Mapping tab
For the Copy stage, the Mapping tab allows you to specify how the output columns are derived, that is, what copied columns map onto them.
The left pane shows the copied columns. These are read only and cannot be modified on this tab.
The right pane shows the output columns for the output link. This has a Derivations field where you can specify how the column is derived. You can fill it in by dragging copied columns over, or by using the Auto-match facility.