SAP Message UAS012 - Not possible to change column "&1" of type "&2"

Diagnosis
You changed the attributes 'key field', 'language-dependent text' or'posting level' of column &v1& of type &v2&. This change is not possiblebecause the database tables concerned already contain data and anautomatic conversion of this data is not supported.

Procedure
To make the change, you must first delete the existing data for thistype.