Solution : https://service.sap.com/sap/support/notes/514777 (SAP Service marketplace login required)
Key words : 
backorder processing, support package 20, missing function, increases performance, back update, distribution documents, terms transactions, /sapapo/bop, /sapapo/bop_updatecapabletopromise, consulting note 426563
Related Notes : 
       
| 609435 | Composite SAP note: Performance in backorder processing | 
| 514327 | BOP termination with error /SAPAPO/RRP 710 | 
| 426563 | CTP: Settings, system behavior and performance (docu) | 
| 420598 | Composite SAP Note for GATP performance in APO 3.1 | 
| 375193 | Backorder processing: Composite SAP note on posting |