Must be configured to use:
fast start failover
snapshot standby
must be in archivelog mode
Flashback database is recommended when using the broker because the broker automatically enables real-time apply.

Oracle database uses past block images to back out changes to the database.
During normal operation oracle occasionally logs these block images in flashback logs, which are written sequentially and not archived.

All files that are needed to completely recover a database from media failure are part of the flash recovery area.
(include archived redo log files, control files, rman backups, flashback logs and the change tracking file)

parameters:
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE =10G;
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST = ‘+DISKn’;
– recommendation is NOT to set this to any other of the dest parameters (
db_create_file_dest
db_create_online_log_dest_n
control_files)

select estimated_flashback_size from v$flashback_database_log and then set
DB_FLASHBACK_RETENTION_TARGET

SHUTDOWN IMMEDIATE
STARTUP MOUNT;
ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=2880 SCOPE=BOTH;
ALTER DATABASE FLASHBACK ON;
ALTER DATABASE OPEN;

select flashback_on from v$database;
If flashback is set to off then all existing flashback logs are deleted automatically.

Default location is $ORACLE_BASE/flash_recovery_area

e.g. alter system set log_archive_dest_n = ‘location=use_db_recovery_file_dest …’;

If DB_RECOVERY_FILE_DEST is specified and no LOG_ARCHIVE_DEST_n is specified, then LOG_ARCHIVE_DEST_10 is implicitly set to the recovery area.
You can override this behavior by setting LOG_ARCHIVE_DEST_10 to an empty string.