Deleting Field Relationships 
From the list of steps, choose Maintain Field Mapping and Conversion Rules.
Position the cursor on the appropriate SAP field.
Choose Remove Source Field. If the SAP field only has one source field assigned to it, the relationship will be deleted. If the SAP field has several source fields assigned to it, a dialog box appears.
Select the source field for which you want to delete the relationship.
Select Choose. The relationship is deleted.
Caution
When you delete the field relationship, the rule assigned by default continues to exist. You should set an initial value in this case.