Solution : https://service.sap.com/sap/support/notes/365424 (SAP Service marketplace login required)
Key words : 
field/structure  optionali_logsys                  atpcs_ret-logsys          xrelease >= 45a, type             optionali_logsys        type      logsys, additional key words atp, function module sd_sales_docu_maintain include, apo backorder processing, import parameter           ref, type      ref, import parameter, sales orders, program error
Related Notes : 
       
| 375193 | Backorder processing: Composite SAP note on posting | 
| 367335 | Delta records during transfer of the BOP results | 
| 367080 | Backorder proc.: temp. quantity assignments not deleted | 
| 365458 | No update of changed orders in APO | 
| 357400 | APO initial provisioning for changed products |