Business Unit Hierarchy

 Hi All, 1. Company. What's the relationship between Company Constant and Address Book. Does every Company need to be defined in Address Book? I am trying to create Company Hierarchy. How can I achieve that. 2. Business Unit What's the relationship between Business Unit (F0006) and Address Book. Does every Business Unit need to be defined in Address Book? I am trying to create Business Unit Hierarchy. Based on the documentation and data dictionary, Level of Detail represents Parent / Child Hierarchy. But when I queried the data in our demo environment , it was not making any sense. 3. Adjustment Period in F0008 table