RMAN duplicate beyond earliest controlfile backup
We have datafile backups (Level 0, Level 1 and archivelogs) going back 20 days, but only have a controlfile backup going back 15 days (as we have a retention policy of 15 days - we have datafile backups going back further as 15 days ago is in the middle of our Level 0 backup cycle).
We wish to clone the database (using RMAN duplicate) from a point-in-time 16 days ago (ie. before the earliest controlfile backup). Is this possible? If so, how?
Thanks
Ian