Solution : https://service.sap.com/sap/support/notes/422122 (SAP Service marketplace login required)
Key words :
neccessary user defined category fields, user defined category field, additional key words j_4kcats, category upgrade report j_4kr25b, support category structures, empty check flag, category structure, report leads, reference field, j_4kcats-j_4kchef = ' '
Related Notes :
| 324765 | category upgrade for systems without categories |
| 203669 | Additions to the upgrade AFS V2.5B |