Cannot set primary key of table using PowerDesigner
To set one or multi properties whose names are used in several tables will be failed, responding the following message in a popup dialog:
If several tables contain same property, which is respected to set as primary
This data item is already used in a primary identifier.
Normalization rules prevent from reusing this data item in another entity.
Then you can check off the feature:
Tools -> Model Options -> Model Settings -> Data Item -> Unique code