RMAN archived redolog backups and maintenance commands are deleting files from the Flash Recovery Area (FRA) when needed. For example:
RMAN> backup archivelog all delete input; delete obsolete;
These commands only delete the files, but not the actual directories when they are empty after the deletion of the files.
When there is an empty subdirectory that is more than 7 days old, they will get purged automatically at the end of controlfile backup. The interval of 7 days is hardcoded and cannot be changed.
For example :
RMAN> backup database including current controlfile;
RMAN> backup current controlfile;