Sample stage: mapping (DataStage)
For the Sample stage, the Mapping options allow you to specify how the output columns are derived, that is, what input columns map onto them.
Click Edit in the Columns section to map columns. View the columns of the sampled data. These are read only and cannot be modified on this tab. This shows the meta data from the incoming link
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 input columns over, or by using the Auto-match facility.