Solution : https://service.sap.com/sap/support/notes/527532 (SAP Service marketplace login required)
Key words : 
changed sales document items, /sapapo/bop_updateperformance solution implement, distribution document, /sapapo/bop, backorder processing, oltp system, updated repeatedly, terms transactions
Related Notes : 
       
| 609435 | Composite SAP note: Performance in backorder processing | 
| 375193 | Backorder processing: Composite SAP note on posting |