ERROR while connecting ORACLE through COGNOS EXPRSS MANAGER !

[mohsin2010]

hi!
I am getting error while connecting to ORACLE through COGNOS EXPRESS MANAGER (under LAUNCH menu IBM cognos administration>configuration>datasource) during connrction to oracle i m getting error

QE-DEF-0285 The logon failed.
QE-DEF-0323 The DSN(ODBC)/ServiceName is invalid. Either the DSN is missing or the host is inaccessible.
RQP-DEF-0068 Unable to connect to at least one database during a multi-database attach to 1 database(s) in:
    testDataSourceConnection

UDA-SQL-0031 Unable to access the "testDataSourceConnection" database.
UDA-SQL-0532 Data Source is not accessible: "XE".
ORA-12154: TNS:could not resolve the connect identifier specified

BME-EX-0144 Trace back:
BmtPlayTransaction.cpp(744): QFException: CCL_RETHROW: BmtPlayTransaction::DoAction
BmtActionsHelper.cpp(475): QFException: CCL_RETHROW: BmtActionsHelper::DoAction
QFSSession.cpp(718): QFException: CCL_RETHROW: QFSSession::ProcessDoRequest()
QFSSession.cpp(716): QFException: CCL_CAUGHT: QFSSession::ProcessDoRequest()
QFSSession.cpp(1535): QFException: CCL_RETHROW: QFSSession::SessionProcessTestConnection()
Source/QE_RsApi.cpp(2064): QFException: CCL_RETHROW: QE
Source/QEI_ConnectionFault.cpp(807): QFException: CCL_THROW: QE


on the same express manager i m able to connect through ODBC connection so why i m getting the above error as well as on the attachment while connecting through ORACLE please help me to get rid of this error  ???

[MFGF]

ORA-12154: TNS:could not resolve the connect identifier specified

This seems to be the error being returned from Oracle - it cannot resolve the connection.  Have you updated the TNSNAMES.ORA file?

MF.