In this process you maintain routings without history.
If you want to document changes to particular fields as change documents, you must make the corresponding setting in Customizing.
You create a routing, valid from a particular key date.
The system creates only one change status for every routing object (header, operation etc.) you create. This status begins on the valid-from date of the change master record and ends on 12/31/9999.
You then create new routing objects or change existing ones in whichever order you like. In each case you enter a key date.
If you change an existing routing object, the system changes this change status. Thus your changes are valid for the whole validity period of the routing object. You can only reconstruct the previous change status, if the system has created the relevant change documents (see prerequisites).