RMAN duplicate database with active database using until clause fails

1.Script to perform rman_duplicate with skip tablespace and perform incomplete recovery using until sequence

run
{
allocate channel trgt1 device type disk connect 'sys/sys123@cvrman';
allocate channel trgt2 device type disk connect 'sys/sys123@cvrman';
allocate channel trgt3 device type disk connect 'sys/sys123@cvrman';
allocate auxiliary channel aux1 device type disk;
allocate auxiliary channel aux2 device type disk;
allocate auxiliary channel aux3 device type disk;
set until sequence 10 thread 1;
duplicate target database to crman
from active database
spfile
set audit_file_dest='/u01/app/orcl/oracle/admin/crman/adump'
set dispatchers='(PROTOCOL=TCP) (SERVICE=crmanXDB)'
set control_files='+DATA','+DATA'
skip tablespace users;
release channel trgt1;
release channel trgt2;
release channel trgt3;
release channel aux1;
release channel aux2;
release channel aux3;
}

2.It fails because until clause accepts only set until time

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of Duplicate Db command at 06/07/2014 12:02:10
RMAN-05501: aborting duplication of target database
RMAN-03015: error occurred in stored script Memory Script
RMAN-06493: only UNTIL TIME clause is allowed when performing a restore from AUTOBACKUP, found: SCN

Solution:-
set until time clause is not applicable with active database