Solution : https://service.sap.com/sap/support/notes/414770 (SAP Service marketplace login required)
Key words : 
sales order delivery schedule, create sales orders, calling function bapi_apo_scheduling, order processing transaction, additional key words, material/plant combination, cif integration model, enables order processing, incorrect system link, error message ag 023
Related Notes : 
       
| 382746 | Collective note: Delivery+transportation scheduling with APO | 
| 322509 | APO integration of scheduling "Exit inserted" |