Diagnosis
You marked the checkbox Reference restriction. This is notallowed for this relationship, since this attribute can only bespecified for relationships of the category "referential" (R), wherethe cardinality of the source entity has the value 'C' (see F1 help forthe checkbox).

System Response
The entered value was reset.

Procedure
Check the relationship attributes and read the documentation for thefield Reference restriction (F1 help on the checkbox).