Size of Redo Generation

Daily 
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SELECT TRUNC (COMPLETION_TIME) "REPORT DATE ",
     COUNT (*) "LOG SWITCH" ,
     ROUND ( (SUM (BLOCKS * BLOCK_SIZE) / 1024 / 1024)) "REDO PER DAY IN MB"
FROM V$ARCHIVED_LOG
GROUP BY TRUNC (COMPLETION_TIME)

ORDER BY 1;

Hourly 
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SELECT TO_CHAR(FIRST_TIME, 'DD-MON-YYYY:HH12:AM') "REPORT DATE AND HOUR ",
     COUNT (*) "LOG SWITCH" ,
     ROUND ( (SUM (BLOCKS * BLOCK_SIZE) / 1024 / 1024)) "REDO PER DAY IN MB"
FROM GV$ARCHIVED_LOG
GROUP BY TO_CHAR(FIRST_TIME, 'DD-MON-YYYY:HH12:AM')

ORDER BY 1;