You can use the COPY_ONLY flag to obtain a full backup without resetting the differential base. This means that any subsequent differential backup you take doesn't refer to the full backup you took with COPY_ONLY. As far as I know, DPM doesn't take differential backups, but it takes only full and log backups.

Transaction log is a different story. If you take a log backup with COPY_ONLY, you won't truncate the transaction log and DPM will back up that portion of the log regularly. What you cannot achieve using COPY_ONLY is a separate copy of the whole log chain. I explain this in a post in my blog that you can find here: http://spaghettidba.com/2014/01/22/copy_only-backups-and-log-shipping/

The post considers log shipping as the "primary" log backup destination, but you can assume it was DPM instead.

Hope this helps