What to do if your flash recovery area is filled with "foreign archive logs"?

One of my databases came to a halt when the flash recovery area filled completely.

It wasn't a problem with space preassure, but merely a condition that made the flash recovery area *seem* full, when it really wasn't.

To clear the archiver stuck condition is easy enough, simply increase the value of db_recovery_file_dest_size, but how to fix the source of the problem?

My flash recovery area was, at the time, filled up with foreign archive logs:

SYS@CDB$ROOT SQL> select * from v$flash_recovery_area_usage;

FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                             0                         0               0          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                         14.04                         0             235          0
BACKUP PIECE                           .06                         0              44          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                  85.8                         0            1558          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

8 rows selected.

To fix this, log on to the database using rman:

rman target / nocatalog

Here you can list the foreign archivelogs:

list foreign archivelogs all;

They were all from may 2023, and they have ended up here since the database was cloned using storage snapshots.

To clear them out of the flash recovery area, you need to first crosscheck them:

RMAN> crosscheck foreign archivelog all;

Then, delete them:

RMAN> delete noprompt foreign archivelog all ;

The crosscheck is important. Without it, Oracle cannot delete the entries from the controlfile, which means that tha v$flash_recovery_area will still be reported as full.
The flash recovery area is not full anymore:

SYS@CDB$ROOT SQL> select * from v$flash_recovery_area_usage;

FILE_TYPE               PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
CONTROL FILE                             0                         0               0          0
REDO LOG                                 0                         0               0          0
ARCHIVED LOG                         18.21                         0             280          0
BACKUP PIECE                           .06                         0              44          0
IMAGE COPY                               0                         0               0          0
FLASHBACK LOG                            0                         0               0          0
FOREIGN ARCHIVED LOG                     0                         0               0          0
AUXILIARY DATAFILE COPY                  0                         0               0          0

8 rows selected.

Documented in Doc ID 1617965.1 "What commands may be used to remove foreign archivelog files?" at Oracle Support.