duplicate

rman duplicate fails with following error,.

RMAN-03002: failure of Duplicate Db command at 09/10/2013 08:29:33

RMAN-05501: aborting duplication of target database

RMAN-03015: error occurred in stored script Memory Script

RMAN-06026: some targets not found - aborting restore

RMAN-06101: no channel to restore a backup or copy of the control file

this is the duplicate script used

run 

{

allocate auxiliary channel ch1 device type disk PARMS="SBT_LIBRARY=/opt/simpana/Base/libobk.so,BLKSIZE=262144,ENV=(CV_mmsApiVsn=2,CV_channelPar=ch1)" ;

allocate channel ch2 type 'sbt_tape' PARMS="SBT_LIBRARY=/opt/simpana/Base/libobk.so,BLKSIZE=262144,ENV=(CV_mmsApiVsn=2,CV_channelPar=ch2)" ;

duplicate target database to rmadb until time "to_date('Aug 28 2013 02:00:00','Mon DD YYYY HH24:MI:SS')";