Solution : https://service.sap.com/sap/support/notes/36407 (SAP Service marketplace login required)
Key words : 
symptom extremely long response times, ensures minimum access times, additional key words transaction, trading partner business area, line-item report, performancereport/report interface, line items occur, optimal database index, partner company code, response times
Related Notes : 
       
| 52539 | COEP Index optimization | 
| 49507 | Reconciliation ledger: Notes on troubleshooting |