Solution : https://service.sap.com/sap/support/notes/663089 (SAP Service marketplace login required)
Key words : 
system writes additional statistical information, significantly larger network load, profile parameter rfc/ext_debugging, abap language elements leave, manually activate external debugging, abap runtime error 7, abap runtime analysis, remote session handling, remote function call, abap server version 6
Related Notes : 
       
| 1319517 | Unicode Collection Note | 
| 920831 | RFC with inactive text language | 
| 886571 | RFC non-Unicode ./. Unicode with illegal text language | 
| 881781 | Unicode/non-Unicode RFC language and code page assignment |