Based on the description could it be that you have different character set settings on server and client. See
http://docs.oracle.com/html/B13804_02/gblsupp.htm[
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Depending on the client installation the character set is defined either in registry under Oracle or as a environment variable.
For the server side, you can check the selected character set for example from
v$parameter
view.
Also the Microsoft version of Oracle client is deprecated so I strongly recommend to use
ODP.NET[
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