Fast-Start Failover is a feature that enables automatic and seamless failover to the standby database in the event of a failure in the primary database. This process eliminates the need for manual intervention during failover and also reconfigures the old primary database automatically to act as the new standby database after failover.

Fast-Start Failover Triggers:

Fast-Start Failover is triggered in the following scenarios:

1. Database Instance Failure
2. Abrupt Shutdown (Shutdown Abort)
3. I/O Errors Causing Datafiles to Go Offline
4. Loss of communication between the standby database, the observer, and the primary database.

Steps to Configure Fast-Start Failover:

1. Configure Standby Redo Logs

Ensure that standby redo logs are configured on both the primary and standby databases. These logs are essential for fast and efficient failover.

2. Set the LogXptMode Property to SYNC

Update the LogXptMode to ensure synchronous communication between the primary and standby databases.

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DGMGRL> EDIT DATABASE 'PRIM' SET PROPERTY 'LogXptMode'='SYNC';
Property "LogXptMode" updated

DGMGRL> EDIT DATABASE 'STAN' SET PROPERTY 'LogXptMode'='SYNC';
Property "LogXptMode" updated

3. Configure the FastStartFailoverTarget Property

Set each database to point to its counterpart as the failover target.

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DGMGRL> EDIT DATABASE 'PRIM' SET PROPERTY FastStartFailoverTarget='STAN';
Property "FastStartFailoverTarget" updated

DGMGRL> EDIT DATABASE 'STAN' SET PROPERTY FastStartFailoverTarget='PRIM';
Property "FastStartFailoverTarget" updated

4. Enable Real-Time Apply

This ensures that redo data is applied to the standby database as soon as it is received, reducing failover time.

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ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE;

5. Switch to MAXAVAILABILITY Mode

Change the protection mode for maximum availability.

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DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;

6. Enable Flashback Database

Flashback Database is critical for automatically reconfiguring the primary database as the new standby database.

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STARTUP MOUNT;
ALTER DATABASE FLASHBACK ON;
ALTER DATABASE OPEN;

7. Enable Fast-Start Failover

Activate Fast-Start Failover in the Data Guard Broker.

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DGMGRL> ENABLE FAST_START FAILOVER;
Enabled.

8. Start the Observer

The observer monitors the primary and standby databases. It is recommended to run the observer on a separate server.

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DGMGRL> CONNECT sys/password@PRIMNET;
DGMGRL> START OBSERVER;
Observer started

9. Verify the Configuration

Check the status of the Fast-Start Failover configuration.

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DGMGRL> SHOW CONFIGURATION VERBOSE;
Configuration
 Name:                TEST
 Enabled:             YES
 Protection Mode:     MaxAvailability
 Fast-Start Failover: ENABLED
 Databases:
   PRIM - Primary database
   STAN - Physical standby database
               - Fast-Start Failover target
Fast-Start Failover
 Threshold: 30 seconds
 Observer:  observer
Current status for "TEST":
SUCCESS

Change the Failover Threshold

You can adjust the failover timeout (default is 30 seconds). For instance, to change it to 45 seconds:

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DGMGRL> EDIT CONFIGURATION SET PROPERTY FastStartFailoverThreshold = 45;

With Fast-Start Failover configured, the observer continuously monitors the primary and standby databases. If a failure occurs in the primary database, the observer initiates failover after the configured threshold (e.g., 30 seconds). The standby database becomes the new primary, and the old primary is reconfigured as the new standby.