RMAN - is it possible to change the tag on an existing backup?

Is it possible to change the tag of an existing backupset?

I have a backupset that doesn't want to restore.  The tag has dots "." in it, which I believe are special characters.  When I try to restore from this tag, rman doesn't seem to like it.

But the backup files exist, they've been crosschecked, and the db incarnation is correct.  Rman just doesn't seem to like any restores attempted from this backupset.  See below.

RMAN> list incarnation;

　

List of Database Incarnations

DB Key Inc Key DB Name DB ID STATUS Reset SCN Reset Time

------- ------- -------- ---------------- --- ---------- ----------