Assignment of Identification Keys for Building Units 
Assignment of Identification Keys for Building Units
Use
A building unit is defined by means of a unique identification key.
The identification key of the building unit can be assigned by the system (internal number assignment), or you can assign it yourself (external number assignment). In Customizing for IS-H, you can specify whether one of these two number assignment methods should be excluded. In Customizing, you can also define the number ranges authorized for internal and external number assignment.
The building unit identification keys must be unique within a client. The system ensures that unique identification keys are always assigned. When internal number assignment is used, the system selects the next number from the internal number range in each case. When external number assignment is used, the system prevents a number that has already been used from being assigned again.
If you work with external number assignment, choose the identification keys such that you can quickly create building units of several organizational units by copying the identification key and making slight changes to the resulting copy. For instance, if the building structure of different floors is similar, you can include the floor number in the identification key. After creating the building units of one floor, you can use these building units as a reference for further building units and only have to change the floor number in the identification key.
If you have defined several institutions in one client and are using external number assignment, you can specify a prefix for each institution which the system places at the start of the identification key of the institutions. This enables you to characterize the building units which belong to the building structure of an institution.