In Oracle 12c Flashback Database must be configured which allow for tracking of changes for the database to revert to.   This article details the steps in enabling flashback database feature.

 

 

1. Logon to server as the oracle software owner.

 

[root@orclc-db1 devadmin]# su – oracle

Last login: Mon Feb 19 18:31:43 UTC 2016 on pts/0

mylinux#

 

2. Open or mount the oracle database.

 

mylinux# sqlplus / as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Tue Feb 20 12:41:43 2016

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup mount

ORACLE instance started.

Total System Global Area 5.1540E+10 bytes

Fixed Size                  2938792 bytes

Variable Size            3.4628E+10 bytes

Database Buffers         1.6777E+10 bytes

Redo Buffers              131276800 bytes

Database mounted.

SQL>

 

3. Set the DB_FLASHBACK_RETENTION_TARGET initialization parameter to time period of recovery, default is 1440 minutes or 1 day.

SQL> alter system set DB_FLASHBACK_RETENTION_TARGET=2880 scope=both;

System altered.

SQL>

 

4. Set the initialization parameter DB_RECOVERY_FILE_DEST_SIZE to a suitable size. NOTE:  This is simple a test system so we area setting the recovery size to 4GB,  a real system will require a larger size.

 

SQL> alter system set db_recovery_file_dest_size = 4g scope=both;

System altered.

 

5. Set the initialization parameter DB_RECOVERY_FILE_DEST to a suitable large enough space one disk.

 

SQL> alter system set db_recovery_file_dest=’ /u04/oradata/ORCL/flash_recovery_area’ scope=both;

System altered.

SQL>

 

6. Ensure that archivelog mode is enabled and enable if not.

 

SQL> archive log list

Database log mode              No Archive Mode

Automatic archival             Disabled

Archive destination            /opt/app/oracle/orcl_db/dbs/arch

Oldest online log sequence     1613

Current log sequence           1633

 

7. Archiving log is not currently enabled, restart the database in mount mode and enable archiving.

 

SQL> shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount

ORACLE instance started.

 

Total System Global Area  549453824 bytes

Fixed Size                  2926616 bytes

Variable Size             268437480 bytes

Database Buffers          272629760 bytes

Redo Buffers                5459968 bytes

Database mounted.

SQL> alter database archivelog;

 

Database altered.

 

SQL>

 

8. Enable flashback for database with ALTER DATABASE command, before opening database.

 

SQL> alter database flashback on;

Database altered.

SQL>

 

9. Alter the database to open.

 

SQL> alter database open;

Database altered.

SQL>

 

10. This completes enabling flashback for your Oracle RDBMS.

 

Larry Catt

OCP