You can add a port to the Sequence Generator transformation as a pass-through port. Pass-through ports are input and output ports that receive input data and return the same data to a mapping without changing it.
You must add at least one input port to the transformation and connect it to an upstream source or transformation before you link the NEXTVAL output port to targets. To add a pass-through port to the transformation, drag a port from an upstream source or transformation in the mapping to the Sequence Generator transformation.