Solution : https://service.sap.com/sap/support/notes/431705 (SAP Service marketplace login required)
Key words : 
prerequisites program error solution maintain, additional key words cif_sl_doc_inbound, error xc 023 occurs, -party scenario, sales orders, backorder processing, integration model, -partybackorder processing, source code
Related Notes : 
       
| 375193 | Backorder processing: Composite SAP note on posting |