How to monitor the amount of redo generated per hour

At customer sites very often I can see the transaction load via the amount of redo which was generated.

For best overview I like to query the amount of redo generated per hour:

SELECT Start_Date,
      Start_Time,
      Num_Logs,
      Round(Num_Logs * (Vl.Bytes / (1024 * 1024)),
            2) AS Mbytes,
      Vdb.NAME AS Dbname
 FROM (SELECT To_Char(Vlh.First_Time,
                      'YYYY-MM-DD') AS Start_Date,
              To_Char(Vlh.First_Time,
                      'HH24') || ':00' AS Start_Time,
              COUNT(Vlh.Thread#) Num_Logs
         FROM V$log_History Vlh
        GROUP BY To_Char(Vlh.First_Time,
                         'YYYY-MM-DD'),
                 To_Char(Vlh.First_Time,
                         'HH24') || ':00') Log_Hist,
      V$log Vl,
      V$database Vdb
WHERE Vl.Group# = 1
ORDER BY Log_Hist.Start_Date,
         Log_Hist.Start_Time;

Sample output:

START_DATE START_TIME NUM_LOGS               MBYTES                 DBNAME
---------- ---------- ---------------------- ---------------------- ---------
2006-01-24 11:00      1                      100                    MYDB
2006-01-24 14:00      2                      200                    MYDB
2006-01-24 16:00      1                      100                    MYDB
2006-01-24 18:00      1                      100                    MYDB
2006-01-24 20:00      5                      500                    MYDB
2006-01-24 21:00      14                     1400                   MYDB
2006-01-24 22:00      11                     1100                   MYDB
2006-01-25 00:00      1                      100                    MYDB
...

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