11g Active Database Duplication

Has anyone used this feature (in version 11.1.0.7) successfully to clone a database between two servers which uses different ASM diskgroups. I am trying to create a clone using following rman script which is failing during restore. Oracle support told me that RMAN first creates a copy backup of the primary database on **source server** and then transfer it to target to build the clone copy. Is that correct? Why it needs to create a copy on source ?

run {
DUPLICATE TARGET DATABASE
TO 'DUPDB'
FROM ACTIVE DATABASE
db_file_name_convert='+DATA1/ORCL','+DATA2/DUPDB' }

Errors during the restore -

Starting backup at 17-DEC-09
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=376 instance=orcl3 device type=DISK channel ORA_DISK_1: starting datafile copy input datafile file number=00007
name=+DATA1/orcl/datafile/index.500.704464441 RMAN-03009: failure of backup command on ORA_DISK_1 channel at 12/17/2009 12:15:47
ORA-19504: failed to create file "+data2" channel ORA_DISK_1 disabled, job failed on it will be run on another channel

Thanks
Manmohan.

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