When using Related Cubes in InterSystems IRIS BI, cubes must be built in the proper order. The One side must be built before the Many side. This is because during build time for the Many side, it looks up the record on the One side and creates a link. If the referenced record is not found on the One side, a Missing Relationship build error is generated. The One side is going to be the independent side of the relationship, AKA the side of the relationship that is referenced by the Many side or the Dependent cube. For example: Patients contain a reference to their Doctor.