Below are the steps for changing the flash recovery area(FRA destination).

1. Check the current FRA destination.

SQL> show parameter db_recovery_file

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /dbaclassdb/oradata/FRA
db_recovery_file_dest_size           big integer 20G


SQL> select name from V$RECOVERY_FILE_DEST;

NAME                                  
--------------------------------------
/dbaclassdb/oradata/FRA               

2. Change db_recovery_file_dest parameter.

SQL> alter system set db_recovery_file_dest='/fradg/oradata/FRA' scope=both;

System altered.


select name from V$RECOVERY_FILE_DEST;
NAME                                   SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES     CON_ID
-------------------------------------- ----------- ---------- ----------------- --------------- ----------
/fradg/oradata/FRA               2.1475E+10          0                 0               0          0

From onwards new files will be created in this new location. However, the flashback logs will be created under the old location.

For the FLASHBACK logfiles to be able to pick up the new ‘db_recovery_file_dest’ location, we just need to disable and enable the flashback, which needs a downtime.

1.  Drop restore point if any

SQL> select GUARANTEE_FLASHBACK_DATABASE,NAME from v$restore_point;
 
GUARANTEE_FLASHBACK_DATABASE     NAME
-------------------------------- -----------------------------
YES                              RESTORE_UPGRDE


SQL > Drop restore point  restore_point RESTORE_UPGRDE ;

2. Turn off and turn on flashback :

ALTER DATABASE FLASHBACK OFF;
ALTER DATABASE FLASHBACK ON;

SEE ALSO:

How to enable flash recovery area in oracle database

How to enable and disable flashback in oracle database

https://dbaclass.com/article/flashback-primary-database-in-dataguard-environment/