After 3 reinstallation that's working. If there is a logical way to understant that I don't see it...
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Problem was the connection string. In the connection string, you have mentioned the driver name of Microsoft ODBC driver (which is 32bit ODBC driver) not Oracle ODBC driver (whose naming convention is "Oracle in <ORACLE_HOME name>").
Ok, thank you for this useful information. It explains my issues