If there are any obsolete transient files available in flash recovery area, then they are automatically deleted by oracle to free up some space. v$recovery_file_dest and v$flash_recovery_area_usage can be queried to identify the same.
If there are no obsolete transient files available then ORA-19804,19809 19815 are thrown.
Hope that helps!
is *NOT* the same as LOG_ARCHIVE_DEST_1= USE_DB_FLASH_RECOVERY_AREA
The latter case is where Oracle can automanage Archivelogs in the FRA
Query V$FLASH_RECOVERY_AREA_USAGE to see if the Archivelogs appear as "registered" in the FRA
Hemant K Chitale