Question about "RMAN-06169:" and Oracle
Try this command to SKIP the offline and corrupted datafiles:

BACKUP DATABASE
    SKIP INACCESSIBLE
    SKIP OFFLINE;



  SKIP INACCESSIBLE: Inaccessible datafiles. A datafile is only considered inaccessible if it cannot be read. Some offline datafiles can still be read because they exist on disk. Others have been deleted or moved and so cannot be
  read, making them inaccessible. 
  
  SKIP OFFLINE: skipping Offline datafiles;


Details: https://docs.oracle.com/cd/B12037_01/server.101/b10734/rcmbackp.htm