RMan hot backup failed with ANS1017E (RC-50)

Hi Experts,

Below is the log got from Oracle ....

RMAN-03009: failure of backup command on t2 channel at 11/06/2012 23:41:57
ORA-19502: write error on file "PLMPROD_HOT_20121106_1tnpl2p5_1_1", block number 2702593 (block size=16384)
ORA-27030: skgfwrt: sbtwrite2 returned error
ORA-19511: Error received from media manager layer, error text:
ANS1017E (RC-50) Session rejected: TCP/IP connection failure

What the cause of this error and how to resolve this problem.

Thanks,
Iscadmin.