Solution : https://service.sap.com/sap/support/notes/881781 (SAP Service marketplace login required)
Key words : 
-ambiguous sap blended code pages, language dependent text data handling, language/code page configuration provided, explicit language/code page assignment, -unicode connection code page based, applies hard wired defaults, asian unification code pages, latin-1 transliteration code page, provide ebcdic code pages, language/code page configuration
Related Notes : 
       
| 1319517 | Unicode Collection Note | 
| 938738 | Syslog CP6: still using ambiguous blended code page | 
| 938737 | Syslog CP6: still using blended code page | 
| 920831 | RFC with inactive text language | 
| 886571 | RFC non-Unicode ./. Unicode with illegal text language | 
| 871945 | Fallback Code Page for Zn Languages in Unicode/nonU RFC | 
| 814707 | Troubleshooting for RFC connections Unicode/non-Unicode | 
| 809279 | RFC non-Unicode to Unicode with unknown text language | 
| 663089 | RFC bit options in transaction SM59 | 
| 547444 | RFC Enhancement for Unicode ./. non-Unicode Connections | 
| 480671 | The Text Language Flag of LANG Fields | 
| 73606 | Supported Languages and Code Pages |