The Mapping Designer generates a field name conflict error when you validate a mapping that has fields with matching names from different transformations. When a field name conflict occurs, you need to ensure that each field has a unique name.
To resolve a field name conflict, you can create a field rule to rename fields. If you create a field rule to resolve a field name conflict, you create the field rule in the upstream transformation.
Alternatively, field name conflict error messages contain a link that you can use to create a field name conflict rule to resolve the field name conflict. A field name conflict rule renames all of the fields from the upstream transformation, not just the fields that cause a conflict.
Field name conflict rules take effect before field rules take effect. Field name conflict rules are only applicable to incoming fields from upstream transformations. Field name conflicts that occur after incoming fields first enter a transformation cannot be corrected by field name conflict rules. For example, you cannot use field name conflict rules to correct field name conflicts that occur due to field rules or activities such as lookup fields. Instead, modify the field rules or transformations that cause the conflict.