Always On Configuration for Automatic Failover

2 Server Setup

Server	Role	Availability Mode	Failover Mode	Connections in Primary Role	Readable Secondary	Seeding Mode	Session Timeout	Endpoint URL
DB01	Primary	Synchronous commit	Automatic	Allow all connections	No	Manual	180	TCP://<servername>:5022
DB02	Secondary	Synchronous commit	Automatic	Allow all connections	No	Manual	180	TCP://<servername>:5022

3 Server Setup

Server	Role	Availability Mode	Failover Mode	Connections in Primary Role	Readable Secondary	Seeding Mode	Session Timeout	Endpoint URL
DB01	Primary	Synchronous commit	Automatic	Allow all connections	No	Manual	180	TCP://<servername>:5022
DB02	Secondary	Synchronous commit	Automatic	Allow all connections	No	Manual	180	TCP://<servername>:5022
DB03	Secondary	Asynchronous commit	Manual	Allow all connections	Yes	Manual	180	TCP://<servername>:5022

Note:

• Set the Failover Mode to
  AUTOMATIC
• Make the current primary and target secondary replica SYNCHRONOUS_COMMIT
  to avoid any data lost during failover.

Sources:

https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/perform-a-planned-manual-failover-of-an-availability-group-sql-server?view=sql-server-ver15