Where as in 11gR2 as per the docs: Now we can ...need to test this scenario.
Restarting DUPLICATE After a Failure
RMAN automatically optimizes a
DUPLICATE command that is a repeat of a previously failed
DUPLICATE command. The repeat
DUPLICATE command notices which datafiles were successfully copied earlier and does not copy them again. This applies to all forms of duplication, whether they are backup-based (with or without a target connection) or active database duplication. The automatic optimization of the
DUPLICATE command can be especially useful when a failure occurs during the duplication of very large databases.
Locates the datafiles that were successfully duplicated by the initial
Displays a message similar to the following for each datafile that it does not need to duplicate again:
RMAN-05560: Using previous duplicated file /oradata/new/data01.f for datafile 1 with checkpoint SCN of 1654665
Restores only the missing or incomplete datafiles, thereby avoiding re-copying and restoring all the datafiles.
Before you attempt to resume a failed
DUPLICATE operation, you must reset the auxiliary instance to
NOMOUNT mode. One way to do this is to exit RMAN, use SQL*Plus to reset the auxiliary instance to
NOMOUNT mode, start RMAN and then repeat the
DUPLICATE command. If you do not want RMAN to automatically recover from a failed
DUPLICATE operation, specify the keyword
NORESUME to disable the functionality. Using the keyword
NORESUME in the first invocation of
DUPLICATE prevents a subsequent
DUPLICATE command for the new database from using this automatic optimization.