SAP Message VP444 - Function & is defined in the header and not deletable here

Diagnosis Header partners cannot be deleted at item level. INCLUDE 'NA_NO_PROCESSING_1' OBJECT DOKU ID TX LANGUAGE D Procedure Delete the partner at header level. If the partner function &V1& inCustomizing is not defined as a compulsory functionfor the document header and is marked as alterable, it can be deleted atheader level. The entries present at item level in this partnerfunction are then automatically deleted.