SQL> select * from v$flash_recovery_area_usage;

FILE_TYPE PERCENT_SPACE_USED
------------------------------------------------------------ ------------------
PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
------------------------- ---------------
CONTROL FILE 0
0 0

REDO LOG 0
0 0

ARCHIVED LOG 92.64
0 229


FILE_TYPE PERCENT_SPACE_USED
------------------------------------------------------------ ------------------
PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
------------------------- ---------------
BACKUP PIECE 7.29
0 2

IMAGE COPY 0
0 0

FLASHBACK LOG 0
0 0


FILE_TYPE PERCENT_SPACE_USED
------------------------------------------------------------ ------------------
PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES
------------------------- ---------------
FOREIGN ARCHIVED LOG 0
0 0


7 rows selected.

1.alter system set DB_RECOVERY_FILE_DEST_SIZE=20g;

2.delete in OS, then

crosscheck archivelog all;
delete noprompt expired archivelog all;