Solution : https://service.sap.com/sap/support/notes/394471 (SAP Service marketplace login required)
Key words : 
structure /sapapo/cif_sl_doc_excomponent                  component typesrcps                      /sapapo/char1 structure /sapapo/cif_sl_doc_ex_xcomponent                  component typesrcps                      bapiupdate structure                  /sapapo/cif_sl_doc_headcomponent                  component typerule_evaluation            /sapapo/char1 structure                  /sapapo/cif_sl_doc_head_xcomponent                  component typerule_evaluation            bapiupdatecreate, component                  component typerule_exec                  char1extend structure cif_sl_hx, program lcavef05press 'create' buttontitle include lcavef05 type, component                  component typesrcps                      char1extend, press 'create' buttonprogram lcavef04title include lcavef04release = 31i, component                  component typesrcps                      bapiupdateadd, component                  component typerule_exec                  bapiupdatealso extend, /sapapo/bop_updatebackorder processing, /sapapo/bop, press 'maintain' buttonmessage class
Related Notes : 
       
| 402346 | Backorder processing: no update in R/3 | 
| 400662 | Backorder processing: Configuration characteristics | 
| 399547 | Backorder processing: Requested quantity is doubled | 
| 375193 | Backorder processing: Composite SAP note on posting |