SQL Server Standard: understanding Basic Availability Groups (BAG)

Tue, 27 Jan 2026 00:00:00 +0000

TL;DR

Basic Availability Groups (BAG) give SQL Server Standard edition users high availability similar to the Always On AG of the Enterprise edition, but with significant limitations:

One group per instance.
One database per group.
No reads on the secondary replica.
No backups on the secondary.
Two nodes maximum, primary and secondary.

For a long time, using Always On Availability Groups required an Enterprise licence, leaving Standard edition users with Database Mirroring. Since SQL Server 2016, Microsoft has offered Basic Availability Groups (BAG) as the replacement for mirroring in the Standard edition.

Always On: mastering the timeouts

Tue, 27 Jan 2026 00:00:00 +0000

TL;DR

To avoid spurious failovers in an Always On environment, adjust these settings:

Lease Timeout: raise it if your server goes through CPU load spikes.
HealthCheck Timeout: raise it if your server is slow to answer diagnostic requests.

When you run AlwaysOn Availability Groups, it is not unusual to get spurious failovers while your system is working perfectly well.

It tends to happen at night, and more rarely during the day. The most common cause is a temporary unavailability of the system, which makes the cluster health checks time out. A typical example is a VM freeze while backup software takes a snapshot.

AlwaysOn AG on Rudi Bruchez

SQL Server Standard: understanding Basic Availability Groups (BAG)

Always On: mastering the timeouts