ORA-03135: connection lost contact
Cause:
1) Server unexpectedly terminated or was forced to terminate.
2) Server timed out the connection.
Action:
1) Check if the server session was terminated.
2) Check if the timeout parameters are set properly in sqlnet.ora.
Reference: http://docs.oracle.com/cd/B28359_01/ser ... #ORA-03135
ORA-03135 occurs when we try to connect oracle database and the connection gets time out. ORA-03135 can also be caused by the firewall when connecting remotely.
To resolve ORA-03135 exception we need to increase the value of the expire_time parameter in the SQLNET.ORA file. SQLNET.ORA file is located under $ORACLE_HOME/network/admin/. If possible set to SQLNET.EXPIRE_TIME = 10. And retry the backup.