Rman backup falis with RMAN-00601 fatal error in recovery manager

Rman backup fails with fatal error.
In the log we can see the connection was terminated from db level.

channel d12: starting compressed full datafile backup set
channel d22: finished piece 1 at 05-JUL-14
RMAN-06900: WARNING: unable to generate V$RMAN_STATUS or V$RMAN_OUTPUT row
RMAN-06901: WARNING: disabling update of the V$RMAN_STATUS and V$RMAN_OUTPUT rows
ORACLE error from target database:
ORA-03135: connection lost contact
Process ID: 31173
Session ID: 494 Serial number: 62117
...
...
..
channel d13: backup set complete, elapsed time: 01:59:05
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00601: fatal error in recovery manager
RMAN-03004: fatal error during execution of command

++ It looks like some one killed the inactive sessions in the db level.But the backup from RMAN was ran due to OS process,When we check the size of backup and validating backup it was convincing that backup ran successfully.So i ignored this fatal error and from next run it was not showing this error.