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Don Burleson Blog

Flashback Database tips

Oracle Database Tips by Donald BurlesonMay 11, 2015

Question: What is Oracle flashback database? How can I use Oracle flashback database in an OLTP shop?

Answer: Oracle flashback database is an extension of the "rollback" functionality, allowing the DBA to flashback a table to a specific date in history. With Oracle flashback, the length of the flashback recovery is determined by the storage dedicated to Oracle UNDO and the settings for flashback database parameters.

Oracle flashback database is implemented via the flashback database command. Flashback database allows you to quickly bring your database to a prior point in time by undoing all of the changes that have taken place since that time. The Oracle database flashback process is fast, because you do not need to restore the backups.

Oracle flashback database can also be used in end-user applications. This use of Oracle flashback database allows selected end-users to flashback their own data tables to any point in time that they desire, without DBA intervention.

Some of the newer features of flashback database include:

Oracle's Flashback Database

Oracle's Flashback Standby Database

Oracle's Flashback Reinstantiation

Oracle's Flashback Drop

Oracle's Flashback Table

Oracle's Flashback Row History

Oracle's Flashback Transaction History

More details on these key Oracle flashback database features is available HERE.

Perform Flashback Database

After completing the functional and technical testing, the database must be restored to the state just after the upgrade is completed. The following procedure illustrates performing the Flashback Database.

SQL> SHUTDOWN IMMEDIATE

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> STARTUP MOUNT

ORACLE instance started.

Total System Global Area 551165952 bytes

Fixed Size 2230232 bytes

Variable Size 373295144 bytes

Database Buffers 171966464 bytes

Redo Buffers 3674112 bytes

Database mounted.

SQL> FLASHBACK DATABASE TO SCN 9294723;

SQL> ALTER DATABASE OPEN RESETLOGS;

Database altered.

SQL>

Now, we query the dynamic view v$session_longops view to monitor the progress of the Flashback Database. Another method is to monitor the instance's alert log file.

$ cd /u01/app/oracle/diag/rdbms/t1c1/T1C1/trace

$ tail -f alert_T1C1.log

Flashback Restore Start

Flashback Restore Complete

Flashback Media Recovery Start

Serial Media Recovery started

Recovery of Online Redo Log: Thread 1 Group 6 Seq 3 Reading mem 0

Mem# 0: +DATA/t1c1/onlinelog/group_6.266.846267799

Mem# 1: +FRA/t1c1/onlinelog/group_6.260.846267803

Incomplete Recovery applied until change 9319751 time 05/03/2014 07:23:44

Flashback Media Recovery Complete

Completed: flashback database to scn 9319750

Disable Flashback Database

Now, we disable Flashback Database. The disable command terminates the Flashback background process RVWR and deletes existing Flashback logs stored at Fast Recovery Area (FRA).

SQL> ALTER DATABASE FLASHBACK off;

Database altered.

SQL> SELECT flashback_on FROM v$database;

FLASHBACK_ON

------------------

SQL>

See our additional notes on Oracle flashback database.