AlwaysOn Basic Availability Groups (BAGs) are available with SQL Server 2016 and 2017 Standard edition. The functionality is generally the same as database mirroring (which has been deprecated). This feature replicates transactions to a database on a secondary server, and is useful for disaster recovery should something happen to the primary server.
If you have a database that requires an extra layer of protection or ‘BAG of tricks’, deploying a Basic Availability Group is useful for providing disaster recovery and high availability for the one database. Also there is major cost savings since it is not necessary to purchase SQL Enterprise edition…this can be done in Standard edition of SQL Server.
BAGs provide a failover environment for only one database, and there can only be two replicas in the group. Replication can be synchronous or asynchronous, and there is no read access, no backups and no integrity checks on the secondary. The secondary replica remains inactive unless there is a failover, and Basic AGs can remain on-premises or span from on-prem to Azure.
Read on for the two methods.