Enable Flashback

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup mount;
ORACLE instance started.
Total System Global Area 184549376 bytes
Fixed Size 1300928 bytes
Variable Size 157820480 bytes
Database Buffers 25165824 bytes
Redo Buffers 262144 bytes
Database mounted.

SQL> alter database archivelog;
Database altered.

SQL> alter system set DB_FLASHBACK_RETENTION_TARGET=4320;
System altered.

SQL> alter system set DB_RECOVERY_FILE_DEST_SIZE=536870912;
System altered.

SQL> alter system set DB_RECOVERY_FILE_DEST='/u02/fra';
System altered.

SQL> alter database flashback on;
Database altered.

SQL> alter database open;
Database altered.