Solution : https://service.sap.com/sap/support/notes/416049 (SAP Service marketplace login required)
Key words : 
sapservx /general/r3server/abap/note, additional preformance improvement, bapilogsys data element, microsoft sql server, wx3k000266                        wx4k000421                        cxik000184, wx4k000403                        wx4k000421                        cx4k000559, performance problems due, long access times, system field element, database utility tool
Related Notes : 
       
| 458136 | IDoc: dup. Idocs in tRFC inbound processing w/ run. errors | 
| 440735 | Unnecessary queue dependencies in APO outbound processing | 
| 438015 | Latest qRFC version and supplement for 3.x, 4.x, 6.10, 6.20 | 
| 420964 | Outbound queues despite use of input queues | 
| 419178 | Release of the queue manager/sapapo/cq | 
| 400330 | Outbound Scheduler/qOUT Scheduler |