Solution : https://service.sap.com/sap/support/notes/1135878 (SAP Service marketplace login required)
Key words : 
sap data    dictionary - defaults, directory /tmp/unload/<sid>, kernel release 46d, code page conversions, code page conversion, function exec_cached_fetch    error, /tmp/<sid>, conversion error, sap database, error message
Related Notes : 
       
| 500950 | iSeries: R/3 EBCDIC --> ASCII Codepage Conversion Doc. |