All Oracle Error CodesOracle DBA Forum

NNL-00005:

no server has been set. Use the "SET SERVER" command first
Cause: The user attempted to issue a command which requires that a default managed Oracle Names server be set first.
Action: Use the SET SERVER command to set your default server, then reissue the command. Alternatively, if the command allows, re-issue it with a specific server name so the control program does not need to use the default.