All Oracle Error Codes
Oracle DBA Forum
osnrntab: connect to host failed, unknown ORACLE_SID
The invoked Unix two-task driver failed to find an entry in oratab for the sid you supplied.
First, check whether you have read access to oratab, and see if the desired sid is there. Add an entry to oratab for the desired sid, if necessary.
Rman and 10.1.0.4