Solution : https://service.sap.com/sap/support/notes/1066323 (SAP Service marketplace login required)
Key words : 
0000000000000a  rfc ==== delta 1   2 regh             0000000000000a  rfc ==== delta 0   2 log  confirm line 0 info 0a  rfc > rfcsys_convert [1] working, t_tabelle1a  rfc ti 0 imp_xtyp usedlen 10092a  rfc ==== delta 0   2 reg, multilanguagea  rfc >         language offset 997g  rscplcgetctry, system converts character-type data, sap code page determined, sap code page c1, sap code page c2, rfc/ignore_mdmp_to_rfclib reason, rfc/ignore_mdmp_to_rfclib = 1does, rfc/ignore_mdmp_from_rfclib = 1does
Related Notes : 
       
| 1319517 | Unicode Collection Note | 
| 1021459 | Conversion behavior of the RFC library | 
| 647495 | RFC for Unicode ./. non-Unicode Connections | 
| 547444 | RFC Enhancement for Unicode ./. non-Unicode Connections |