& & is already assigned to documents

What causes this issue?

&V1& &V2& is already used in documents.

System Response

In order to ensure data consistency between a document and a license,
the process of changing licenses, depending on the document category of
the documents that have been assigned, can be strongly limited.

How can this happen?

If an order has already been assigned to the present license, it is no
longer possible to change certain field contents or to delete certain
entries.

Error message extract from SAP system. Copyright SAP SE.