Archive Logs filling up Flash Recovery Area (FRA) space
Oracle will automatically delete obsolete files. In general, you should not have to manually delete anything.


  An important part of RMAN maintenance is deleting backups that are no longer needed. If you configure a fast recovery area, then the database automatically deletes unneeded files in this area automatically


From Overview of RMAN Backup and Repository Maintenance

First, determine if you are running out of space. For example using the following query (sample output included):

SELECT * FROM V$RECOVERY_FILE_DEST;

NAME            SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES
--------------  ----------- ---------- ----------------- ---------------
/mydisk/rcva     5368709120 109240320             256000              28


If you are running out of space you have to either decrease your retention policy or increase the size of your FRA.