Let us first understand Flashback Database :
With Flashback Database technology of Oracle, you can quickly bring your database to an earlier point in time by undoing all changes that took place since that time. This operation is fast because you do not need to restore backups.
Oracle Flashback Database, lets you quickly recover the entire database from logical data corruptions or user errors.
It works like a rewind button.
We can apply flashback logs at any point of time and can recover database from logical errors.
To enable Flashback Database, you set up a flash recovery area, and set a flashback retention target, to specify how far back into the past you want to be able to restore your database with Flashback Database.
Now, how it helps in the Data Guard environment.
- It is the strong alternative in restoring and recovering Primary Database
- When we use the failover method, we can reinstate primary database if we have enabled flashback database.
- An alternative to delaying the application of redo to protect against user errors or logical corruptions
Basically, flashback database helps us in following scenarios.
- Fast Start Failover: Flashback database is used in Fast Start Failover, we must enable flashback database and set fast recovery area in Primary and Target standby database for fast-start failover before we enable fast-start failover
- Snapshot Standby database: To convert Physical standby database to snapshot standby database we must configure Flash recovery area and size. And if flashback database is not enabled it will be enabled by Oracle when we convert physical standby database to snapshot standby database.
A snapshot standby database will be flashed back to the point when it was created by flashing back the database to the guaranteed restore point to convert it back to a physical standby database.
To know more about the snapshot standby database :
Configuring Flashback Database :
In below steps, we can configure the flashback database.
Step 1: Configure fast recovery area :
SQL> show parameter db_recovery NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ db_recovery_file_dest string /u01/oracle/fast_recovery_area
Step 2: Set db_flashback_retention_target
SQL> ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=2880; System altered.
Step 3: Enable flashback database :
SQL> ALTER DATABASE FLASHBACK ON; Database altered.
You can check flashback database is enabled or not from the v$database view.
SQL> select flashback_on from v$database; FLASHBACK_ON ------------------ YES
Enabling flashback in data guard environment gives many benefits.
One of them is using it as an alternative to APPLY DELAY.
Yes..!! There are many lots of companies who manage the standby database with different delays. Like log should be applied to the standby database after the specified amount of time so we can recover from user error.
Here, in this scenario Flashback works efficiently. Like pressing rewind button…!!!
We can recover from any user error or logical data corruption.
We can flashback the database to any arbitrary time in provided retention.
Another benefit of using flashback database in real time query is the Oracle Data Guard real-time apply feature reduces failover time. Flashback Database protects a physical standby database from logical data corruption and user error.
Stay tuned for More articles on Oracle DataGuard
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