How much DB undo generated

Create Or Replace Force View Sys.Av_db_undo_generated (Rundate,
                                                       Day,
                                                       Logswitch,
                                                       "REDO PER DAY (MB)"
                                                      )
As
   Select   Trunc (Completion_time) Rundate,
            To_char (Trunc (Completion_time), 'DAY') Day, Count (*) Logswitch,
            Round ((Sum (Blocks * Block_size) / 1024 / 1024)
                  ) "REDO PER DAY (MB)"
       From V$archived_log
   Group By Trunc (Completion_time)
   Order By 1 Desc;