Diagnosis
Entity types with storage and use type 4
must be used as to-entity types in one relationship with therelationship type Leading. You can use the from-entity type toprocess the attributes or assignment of additional entity types usingthe relationship type Referencing.
There is either more than one relationship with Leading as therelationship type, or none at all.

System Response
The data model cannot be saved or activated.

Procedure
Make sure that there is exactly one relationship with the relationshiptype Leading.