Check backup status of a Database

So you're wondering if your database is stuck in hot backup mode. This query will tell you if that is the case:

  SELECT t.name, d.file# as, b.status     
  FROM V$DATAFILE d, V$TABLESPACE t, V$BACKUP b      
  WHERE d.TS#=t.TS# AND b.FILE#=d.FILE#;

Taken from here