It’s very simple to perform failover using data guard broker. If primary database is unavailable, we can activate standby using below method. Note, in a failover, we have lost primary. Full article link is here: https://www.support.dbagenesis.com/post/data-guard-broker-failover

1. DATA GUARD
BROKER
FAILOVER

2. Crash the primary
Let us simulate failure. We will kill the PMON process at OS level.

3. Failover to proddb_st
connect to standby database proddb_st (as primary crashed or not
available) and failover to standby proddb_st

4. Rebuild primary after failover
Post failover, there are two methods of rebuilding your failed primary:
Method 1: Rebuild from scratch –> RMAN duplicate
Method 2: Flashback database –> only if Flashback was enabled
Reinstate failed primary
When you use data guard broker, with just one command, the
primary can be rebuilt. Start the failed primary server, in this
case start proddb server

6. Verify proddb post reinstate
The best part is broker will automatically recover earlier failed primary
proddb, mount the database and start MRP too

7. Switchover to get original configuration
At this stage, you can perform switchover to again get back original
configuration

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