1. Create new DD repository, select the Use Fibre Channel (FC) connectivity check box and specify proxy server that is connected to the DD via FC, and select the same storage unit with "Import existing backups automatically" checkbox enabled;
2. Go to the job setting and map it to the existing backup chain on the "new" DD repository.
3. Go to backups and find your existing backup chain, right click on it and select "Remove from backups";