SAP Message AP139 - You can no longer change the controlling area

Diagnosis
You tried to change the controlling area of an investment programposition, although there are already measures assigned to thisposition.
Making this change is not possible. The program position and themeasures always have to belong to the same controlling area.

System Response
Changing the controlling area is not allowed.

Procedure
If you want to change the controlling area, you first have to deleteall of the assignments of measures to the position.