Solution : https://service.sap.com/sap/support/notes/493656 (SAP Service marketplace login required)
Key words : 
abap workbench -> ddic objects -> development -> dictionary1, table   /sapapo/cif_sl_doc_ex               field   basme3, backorder processing run, sales order items, connected oltp system, source code corrections, development class, /sapapo/cif_sl_doc_ex, source code, field label
Related Notes : 
       
| 497172 | Backorder processing: several request schedule lines | 
| 495273 | Backorder processing: several request schedule lines | 
| 495171 | Error assigning the requirement quantity and req. del. date | 
| 375193 | Backorder processing: Composite SAP note on posting |