Solution : https://service.sap.com/sap/support/notes/119881 (SAP Service marketplace login required)
Key words : 
business volume data havevery long runtimes, additional key words subsequent settlement, recompilation ofbusiness volume data, business volume data, volume-based rebate, purchase order items, period condition records, period condition record, symptom report rwmbon08, business volume
Related Notes : 
       
| 333914 | Subsequent settlement: performance collective note | 
| 40147 | Collective note: Subsequent settlement (Purch.) Release 3.0 |