I believe post defining the NLS_LANG variable on the UNIX box, service processes on the box were restarted. If not, please do so.
Also, please define the same environment variable at DIS process level. (DIS->Processes->Environment Variables)
Thanks and regards
Thank you Akshay, it looks like that unix variable, connection details and DIS default codepage was not enough. After I add the NLS_LANG to the process environment variables all works now!