Source : http://lefterhs.blogspot.co.id/2012/07/archived-log-generation-volume-and.html
V$ARCHIVED_LOG displays information about the archived logs generated by your database and haven’t yet aged out from your control file.
We are going to use this view to generate a report, displaying some useful information about it.
BLOCKS column stores archived log’s size in blocks, BLOCK_SIZE stores block size in bytes, so if we multiply them (BLOCKS*BLOCK_SIZE) we get its size in bytes.
ARCHIVED indicates whether the log is archived and DELETED whether RMAN has deleted it.
The following query displays per day the volume in MBytes of archived logs generated, deleted and of those that haven’t yet been deleted by RMAN.