HI i am using OCCI library to connect my c++ code on Linux platform to oracle database when i m creating connection using env=Environment::createEnvironment(); env.createConnection("scott","tiger",); here i left blank database name parameter when i don't specify database it connect to oracle but dint provide access to all databases but when i specify database name i.e. env.createConnection("scott","tiger","MYDB"); it shows error that ORA-12154:TNS :could not resolve the connect identifier specified i have checked my tnsnames.ora file i have specified hame thier proprly and from some other client i am able to connect to oracle server using this names using sql developer what could be problem pls help me to find out solution Thanks and Regards Rahul