Solution : https://service.sap.com/sap/support/notes/628948 (SAP Service marketplace login required)
Key words : 
symptom performance improvement, source code corrections, related correction notes 542191, correction note 542191, apo update, sales orders, needed anymore, solution implement, prerequisites, implementation
Related Notes : 
       
| 610704 | Composite SAP note: Performance of SD document update | 
| 609435 | Composite SAP note: Performance in backorder processing | 
| 578625 | BOP: 'Rejected' status inadvertently set | 
| 578278 | BOP: 'Rejected' status | 
| 542191 | Processing rejected items | 
| 420606 | Collective SAP Note for GATP performance in APO 3.0A | 
| 420598 | Composite SAP Note for GATP performance in APO 3.1 | 
| 375193 | Backorder processing: Composite SAP note on posting |