Archived Redo Logs - Who is making too many

Query to determine what user, suddenly, is making too many archived redo logs:

  SELECT s.sid, s.serial#, s.username, s.program, i.block_changes 
  FROM v$session s, v$sess_io i
      WHERE s.sid = i.sid   
      ORDER BY 5 desc, 1, 2, 3, 4

The one(s) that is(are) on top, are the guilty user(s).