.::: Steps for Installing SQL Server AlwaysOn Availability Groups :::.

SQL Server 2012's new features and enhancements include Always On SQL Server Failover Cluster Instances and Availability Groups which provides a set of options to improve database availability, Contained Databases which simplify the moving of databases between instances, new and modified Dynamic Management Views and Functions, programmability enhancements including new spatial features, metadata discovery, sequence objects and the THROW statement, performance enhancements such as ColumnStore Indexes as well as improvements to OnLine and partition level operations and security enhancements including provisioning during setup, new permissions, improved role management, and default schema assignment for groups.


1. Add Windows Failover Clustering (WSFC) to each replica (server)

COnfigure Must using login Join Domain

2. Configure WSFC on your primary replica

3. Configure SQL Server on each replica

4. Configure Logins & Replicas

// executte remote access to all node

exec sp_configure 'remote access',1;

go

reconfigure;

go

5. Install AlwaysOn

6. check alwayson

Testing Failover include log 

https://teguhth.blogspot.com/2021/10/testing-failover-always-on-sql-server.html 
tutorial
full install https://www.sqlrx.com/steps-for-installing-sql-server-alwayson-availability-groups/
join only https://www.mssqltips.com/sqlservertip/5283/add-a-sql-server-database-to-an-existing-always-on-availability-group/