Solution : https://service.sap.com/sap/support/notes/546868 (SAP Service marketplace login required)
Key words :
choose menu option 'set types/attributes -> transport -> include, system automatically extends messaging bdocs product_mat, system issues error message crmxif_prod003, added user-defined segments, user-defined set type &, 'create api append' flag, 'maintain set types, customer set type, function module crmxif_prod_cust_sett_map_from, prerequisites crmxif_product_material_save01 solution
Related Notes :
| 428989 | Customer-specific enhancements for data exchange |