How to purge logs by using Flashback feature in Oracle Database
FRA will be purged automatically when free space is needed
Put the archived logs in FRA as well
Use RMAN to make the backups and use RMAN commands (REPORT OBSOLETE / DELETE OBSOLETE) to manage the purging of  backup pieces + archived logs from FRA


From docs: (http://docs.oracle.com/cd/B19306_01/backup.102/b14192/setup005.htm)

The Oracle Flashback Database feature, which provides an convenient alternative to point-in-time recovery, generates flashback logs, which are also considered transient files and must be stored in the flash recovery area. However, unlike other transient files, flashback logs cannot be backed up to other media. They are automatically deleted as space is needed for other files in the flash recovery area.

When Files are Eligible for Deletion from the Flash Recovery Area

There are relatively simple rules governing when files become eligible for deleteion from the flash recovery area:


Permanent files are never eligible for deletion.
Files that are obsolete under the configured retention policy are eligible for deletion.
Transient files that have been copied to tape are eligible for deletion.