1. Summary Step of How to Enable Flashback Database
- Primary
- Shutdown database
- Startup in mount mode
- Enable archive log if it disable
- Enable flashback
- Open database
- Physical Standby
- Cancel Recovery Process
- Shutdown database
- Startup in mount mode
- Enable archive log if it disable
- Enable flashback
- Open database
- Start Recovery Process
2. Detail Step of How to Enable Flashback Database
2.1 Enable Flashback Database on Primary DB
a. Check database whether it was enable or not
SQL>
select instance_name, status from v$instance;
INSTANCE_NAME STATUS
---------------- ------------
DC OPEN
SQL>
select NAME,FLASHBACK_ON from v$database;
NAME FLASHBACK_ON
--------- ------------------
DC NO
b. Set FRA location and size
SQL>
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='+RECO' SCOPE=SPFILE;
ALTER SYSTEM SET db_recovery_file_dest_size=3G SCOPE=SPFILE;
c. Enable flashback
SQL>
shut immediate
startup mount;
alter database archivelog;
alter database flashback on;
alter database open;
d. Flashback Retention
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=4320; # 3 days, in minute
2.2 Enable Flashback Database on Standby DB:
a. Check database whether it was enable or not
SQL>
select instance_name, status from v$instance;
INSTANCE_NAME STATUS
---------------- ------------
DC OPEN
SQL>
select NAME,FLASHBACK_ON from v$database;
NAME FLASHBACK_ON
--------- ------------------
DC NO
b. Set FRA location and size
SQL>
ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='+RECO' SCOPE=SPFILE;
ALTER SYSTEM SET db_recovery_file_dest_size=3G SCOPE=SPFILE;
c. Enable flashback
SQL>
alter database recover managed standby database cancel;
shut immediate
startup mount;
alter database flashback on;
alter database open;
alter database recover managed standby database using current logfile disconnect from session;
d. Flashback Retention
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=4320; # 3 days, in minute
3. Verify Flashback on Both Primary and Standby after Enable it
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination +RECO
Oldest online log sequence 5
Next log sequence to archive 7
Current log sequence 7
SQL> show parameter LOG_ARCHIVE_DEST_1
NAME TYPE VALUE
------------------------------------ ----------- -----------------
log_archive_dest_1 string LOCATION=+RECO
SQL>
select NAME,FLASHBACK_ON from v$database;
NAME FLASHBACK_ON
--------- ------------------
DC YES
SQL>
show parameter DB_FLASHBACK_RETENTION_TARGET
NAME TYPE VALUE
------------------------------------ ----------- -----------------
db_flashback_retention_target integer 4320
SQL>
SQL>
show parameter db_recovery_file_dest
NAME TYPE VALUE
------------------------------------ ----------- -----------------
db_recovery_file_dest string +RECO
db_recovery_file_dest_size big integer 3G
SQL>
4. Test Case
a. Case 1: Perform Flashback Database ToTime on Both Primary and Standby
i. Primary
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
YES
#Create test table:
SQL> Create table test(id nvarchar2(1000));
SQL>
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
#Select From (Primary):
SQL> select * from test;
ID
-------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 11:43:51
25-06-2014 11:43:54
25-06-2014 11:43:57
25-06-2014 11:44:00
10 rows selected.
SQL>
#Select From (Standby):
SQL> select * from test;
ID
-------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 11:43:51
25-06-2014 11:43:54
25-06-2014 11:43:57
25-06-2014 11:44:00
10 rows selected.
SQL>
#Perform flashback database with RMAN
RMAN> shutdown immediate
using target database control file instead of recovery catalog
database closed
database dismounted
Oracle instance shut down
RMAN> startup mount;
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 1235959808 bytes
Fixed Size 2227904 bytes
Variable Size 939524416 bytes
Database Buffers 285212672 bytes
Redo Buffers 8994816 bytes
RMAN> FLASHBACK DATABASE TO TIME "TO_DATE('25-06-2014 11:43:48','DD-MM-YYYY HH24:MI:SS')";
Starting flashback at 25-JUN-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=24 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=26 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=28 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=29 device type=DISK
starting media recovery
archived log for thread 1 with sequence 19 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_19.565.851118079
archived log for thread 1 with sequence 20 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_20.566.851118081
archived log for thread 1 with sequence 21 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_21.567.851118219
archived log for thread 1 with sequence 22 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_22.568.851118221
archived log for thread 1 with sequence 23 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_23.569.851118225
archived log for thread 1 with sequence 24 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_24.570.851118225
archived log for thread 1 with sequence 25 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_25.571.851118229
media recovery complete, elapsed time: 00:00:08
Finished flashback at 25-JUN-14
RMAN> alter database open resetlogs;
database opened
RMAN> alter database open resetlogs;
database opened
RMAN> exit
sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jun 25 12:05:40 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options
SQL> select * from test;
ID
-------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
6 rows selected.
#Note: At standby alert log will show message as below after primary finish open db with resetlogs. This mean that recovery process will stop by itself.
2014-06-25 11:53:35.598000 +07:00
MRP0: Background Media Recovery process shutdown (DGDB)
ii. Standby
SQL> alter database recover managed standby database cancel;
alter database recover managed standby database cancel
*
ERROR at line 1:
ORA-16136: Managed Standby Recovery not active
SQL> shut immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>
rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Wed Jun 25 12:02:19 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database (not started)
RMAN> startup mount;
Oracle instance started
database mounted
Total System Global Area 835104768 bytes
Fixed Size 2232960 bytes
Variable Size 301993344 bytes
Database Buffers 528482304 bytes
Redo Buffers 2396160 bytes
RMAN>
RMAN>
RMAN> FLASHBACK DATABASE TO TIME "TO_DATE('25-06-2014 11:43:48','DD-MM-YYYY HH24:MI:SS')";
Starting flashback at 25-JUN-14
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=88 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=89 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=90 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=91 device type=DISK
starting media recovery
archived log for thread 1 with sequence 19 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_19.582.851118075
archived log for thread 1 with sequence 20 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_20.581.851118079
archived log for thread 1 with sequence 21 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_21.358.851118217
archived log for thread 1 with sequence 22 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_22.480.851118221
archived log for thread 1 with sequence 23 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_23.271.851118221
archived log for thread 1 with sequence 24 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_24.478.851118223
archived log for thread 1 with sequence 25 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_25.419.851118225
media recovery complete, elapsed time: 00:00:14
Finished flashback at 25-JUN-14
RMAN>
RMAN>
RMAN> alter database open;
database opened
RMAN> exit
Recovery Manager complete.
[oracle@ol6211gr2dr ~]$
[oracle@ol6211gr2dr ~]$
[oracle@ol6211gr2dr ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jun 25 12:04:42 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options
SQL> @start_recover
Database altered.
SQL> ;
1* alter database recover managed standby database using current logfile disconnect from session
SQL>
SQL> select * from test;
ID
--------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
6 rows selected.
b. Case 2: Perform Flashback Database on Both Primary and Standby
By Using Guaranteed Restore Points
i. Create Guaranteed Restore Points on Standby
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
YES
SQL> CREATE RESTORE POINT before_flashback2 GUARANTEE FLASHBACK DATABASE;
SQL> SELECT NAME, SCN, TIME, DATABASE_INCARNATION#,
GUARANTEE_FLASHBACK_DATABASE,STORAGE_SIZE
FROM V$RESTORE_POINT;
NAME
--------------------------------------------------------------------------------
SCN
----------
TIME
---------------------------------------------------------------------------
DATABASE_INCARNATION# GUA STORAGE_SIZE
--------------------- --- ------------
BEFORE_FLASHBACK2
1073762
25-JUN-14 05.28.03.000000000 PM
4 YES 52428800
SQL>
ii. Create Guaranteed Restore Points on Primary
SQL> CREATE RESTORE POINT before_flashback2 GUARANTEE FLASHBACK DATABASE;
Restore point created.
SQL> SELECT NAME, SCN, TIME, DATABASE_INCARNATION#,
2 GUARANTEE_FLASHBACK_DATABASE,STORAGE_SIZE
3 FROM V$RESTORE_POINT;
NAME
--------------------------------------------------------------------------------
SCN
----------
TIME
---------------------------------------------------------------------------
DATABASE_INCARNATION# GUA STORAGE_SIZE
--------------------- --- ------------
BEFORE_FLASHBACK2
1073790
25-JUN-14 05.28.29.000000000 PM
4 YES 52428800
SQL>
insert into test values('BEFORE_FLASHBACK2');
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
insert into test values(TO_CHAR(SYSDATE,'DD-MM-YYYY HH24:MI:SS'));
commit;
alter system switch logfile;
Primary:
SQL> select * from test;
ID
--------------------------------------------------------------------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 12:59:34
25-06-2014 12:59:34
25-06-2014 12:59:35
25-06-2014 12:59:37
25-06-2014 12:59:38
ID
--------------------------------------------------------------------------------
25-06-2014 12:59:41
25-06-2014 12:59:44
25-06-2014 12:59:47
25-06-2014 12:59:50
25-06-2014 12:59:53
after flash
after flash 1
BEFORE_FLASHBACK2
25-06-2014 17:31:06
25-06-2014 17:31:07
25-06-2014 17:31:11
ID
--------------------------------------------------------------------------------
25-06-2014 17:31:14
25-06-2014 17:31:17
25-06-2014 17:31:20
25-06-2014 17:31:23
25-06-2014 17:31:26
25-06-2014 17:31:29
25-06-2014 17:31:32
29 rows selected.
SQL>
iii. Check data on Standby
SQL>
SQL> select * from test;
ID
--------------------------------------------------------------------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 12:59:34
25-06-2014 12:59:34
25-06-2014 12:59:35
25-06-2014 12:59:37
25-06-2014 12:59:38
ID
--------------------------------------------------------------------------------
25-06-2014 12:59:41
25-06-2014 12:59:44
25-06-2014 12:59:47
25-06-2014 12:59:50
25-06-2014 12:59:53
after flash
after flash 1
BEFORE_FLASHBACK2
25-06-2014 17:31:06
25-06-2014 17:31:07
25-06-2014 17:31:11
ID
--------------------------------------------------------------------------------
25-06-2014 17:31:14
25-06-2014 17:31:17
25-06-2014 17:31:20
25-06-2014 17:31:23
25-06-2014 17:31:26
25-06-2014 17:31:29
25-06-2014 17:31:32
29 rows selected.
SQL>
iv. Flashback on Primary
SQL>
rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Wed Jun 25 17:35:02 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: DB (DBID=1614976585)
RMAN> shutdown immediate
using target database control file instead of recovery catalog
database closed
database dismounted
Oracle instance shut down
RMAN> startup mount;
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 1235959808 bytes
Fixed Size 2227904 bytes
Variable Size 1023410496 bytes
Database Buffers 201326592 bytes
Redo Buffers 8994816 bytes
RMAN> FLASHBACK DATABASE TO RESTORE POINT 'BEFORE_FLASHBACK2';
Starting flashback at 25-JUN-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=24 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=27 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=28 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=29 device type=DISK
starting media recovery
archived log for thread 1 with sequence 3 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_3.329.851136987
archived log for thread 1 with sequence 4 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_4.328.851137423
archived log for thread 1 with sequence 5 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_5.327.851137433
archived log for thread 1 with sequence 6 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_6.326.851137937
archived log for thread 1 with sequence 7 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_7.323.851138079
archived log for thread 1 with sequence 8 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_8.320.851138087
archived log for thread 1 with sequence 9 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_9.319.851138539
archived log for thread 1 with sequence 10 is already on disk as file +RECO/db/archivelog/2014_06_25/thread_1_seq_10.322.851139067
media recovery complete, elapsed time: 00:00:12
Finished flashback at 25-JUN-14
RMAN> alter database open resetlogs;
database opened
RMAN>
sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jun 25 17:37:05 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options
SQL> select * from test;
ID
--------------------------------------------------------------------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 12:59:34
25-06-2014 12:59:34
25-06-2014 12:59:35
25-06-2014 12:59:37
25-06-2014 12:59:38
ID
--------------------------------------------------------------------------------
25-06-2014 12:59:41
25-06-2014 12:59:44
25-06-2014 12:59:47
25-06-2014 12:59:50
25-06-2014 12:59:53
after flash
after flash 1
18 rows selected.
SQL>
v. Flashback on Standby
SQL>
rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Wed Jun 25 17:37:51 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: DB (DBID=1614976585)
RMAN> shutdown immediate
using target database control file instead of recovery catalog
database closed
database dismounted
Oracle instance shut down
RMAN> startup mount;
connected to target database (not started)
Oracle instance started
database mounted
Total System Global Area 835104768 bytes
Fixed Size 2232960 bytes
Variable Size 301993344 bytes
Database Buffers 528482304 bytes
Redo Buffers 2396160 bytes
RMAN> FLASHBACK DATABASE TO RESTORE POINT 'BEFORE_FLASHBACK2';
Starting flashback at 25-JUN-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=91 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=92 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=95 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=96 device type=DISK
starting media recovery
archived log for thread 1 with sequence 5 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_5.472.851137423
archived log for thread 1 with sequence 6 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_6.470.851137929
archived log for thread 1 with sequence 7 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_7.477.851138069
archived log for thread 1 with sequence 8 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_8.452.851138077
archived log for thread 1 with sequence 9 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_9.469.851138529
archived log for thread 1 with sequence 10 is already on disk as file +RECO/dgdb/archivelog/2014_06_25/thread_1_seq_10.474.851139057
media recovery complete, elapsed time: 00:00:08
Finished flashback at 25-JUN-14
RMAN>
sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Wed Jun 25 17:39:17 2014
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options
SQL> @start_recover;
Database altered.
SQL> ;
1* alter database recover managed standby database using current logfile disconnect from session
SQL>
SQL> select * from test;
ID
--------------------------------------------------------------------------------
25-06-2014 11:43:38
25-06-2014 11:43:39
25-06-2014 11:43:39
25-06-2014 11:43:44
25-06-2014 11:43:45
25-06-2014 11:43:48
25-06-2014 12:59:34
25-06-2014 12:59:34
25-06-2014 12:59:35
25-06-2014 12:59:37
25-06-2014 12:59:38
ID
--------------------------------------------------------------------------------
25-06-2014 12:59:41
25-06-2014 12:59:44
25-06-2014 12:59:47
25-06-2014 12:59:50
25-06-2014 12:59:53
after flash
after flash 1
18 ows selected.
5. Maintenance
a. Sizing FRA
SQL> ALTER SYSTEM SET db_recovery_file_dest_size=2G SCOPE=SPFILE;
b. Flashback Retention
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=4320; # 3 days, in minute
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=15; # 15 minute
c. Check FRA usage
SQL>
SELECT Sum(PERCENT_SPACE_USED) FROM V$FLASH_RECOVERY_AREA_USAGE;
SELECT * FROM V$FLASH_RECOVERY_AREA_USAGE;
SELECT * FROM V$RECOVERY_FILE_DEST;
d. Estimating Disk Space Requirements for Flashback Database Logs(After Enable Flashback)
SQL>
SELECT ESTIMATED_FLASHBACK_SIZE FROM V$FLASHBACK_DATABASE_LOG;
Good Luck !!!
