Error: External loader is not supported for direct flat files. Target instance <target instance name>.
In the session properties, you chose an external loader connection for a target based on a flat file target definition. This might have happened if you chose an external loader connection for a target based on a relational target definition and then in the Designer, you changed the relational target definition to a flat file definition.
In the Designer, change the flat file target definition to a relational target definition. You can only choose an external loader connection when the target is based on a relational target definition.