Solution : https://service.sap.com/sap/support/notes/367335 (SAP Service marketplace login required)
Key words : 
symptom temporary quantity allocations, additional key words atp, optional import parameter iv_logsys, attached source code corrections, status persistent created, choose atpcs-logsys, function module atp_confirmation_data_set, choose logsys, function module, backorder processing
Related Notes : 
       
| 389027 | Initial supply terminates with error | 
| 376127 | Temp.qty assgts retained after BOP result transfer | 
| 375193 | Backorder processing: Composite SAP note on posting | 
| 368622 | Initial transaction GUID | 
| 367080 | Backorder proc.: temp. quantity assignments not deleted | 
| 365458 | No update of changed orders in APO | 
| 365424 | Incorrect updating of APO backorder processing in R/3 |