Oracle备份RMAN Failed With RMAN-06004 ORA-03135 ORA-03114

Oracle Server - Enterprise Edition - Version: 8.1.7.0 to 11.1.0.7 - Release: 8.1.7 to 11.1
Information in this document applies to any platform.
SymptomsRMAN failed with following errors

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-06004: ORACLE error from recovery catalog database: ORA-03135: connection lost contact
ORACLE error from recovery catalog database: ORA-03114: not connected to ORACLE

Cause+ Problem could be caused by unexpected termination of server or was forced to terminate or server timed out during the connection.

Solution+ Is the rman catalog Database running on a different system than the Target Database?
If so, verify with the System Administrators what the TCP/IP timeout is set to. If there is any firewall between two systems, set the value of SQLNET.EXPIRE_TIME to less than the TCP timeout value of the firewall.

+ Increase the value of SQLNET.EXPIRE_TIME in the sqlnet.ora file on both target servers if no firewall exists between two systems.

+ Increase the value of keepalive interval