Diagnosis
You currently have multiple assignments between plants and assortmentsand want to change the setting to a 1:1 assignment.

System Response
The change is not permitted because plants are already assigned toassortments and it would therefore cause inconsistencies.

Procedure
Delete all the assignments between plants and assortments. You can thenreset the switch to the 1:1 assignment.
You should note, however, that deleting the assignments may mean thatmaterials are no longer listed in plants.