I received alerts saying my availability group was out of synch. Looking at the dashboard shows one of the replicas not synchronizing.
To setup alerts so you know what is going on, read my previous post about setting up alerts for Availability Groups. https://jimsalasek.com/2018/08/15/create-alerts-for-availability-groups/
This is what the dashboard is showing.
Looking in the warning messages, it shows the following messages, which are actually straight forward for a change.
Always On Availability Groups data movement for database 'SurveillanceLogServer' has been suspended for the following reason: "system" (Source ID 5; Source string: 'SUSPEND_FROM_RESTART').
To resume data movement on the database, you will need to resume the database manually. For information about how to resume an availability database, see SQL Server Books Online.
Either a database administrator or the system has suspended data synchronization on this availability database.
The fix is relatively simple, we just need to resume HADR using the command below for all of the databases that are out of sync.
ALTER DATABASE [SurveillanceLogServer] SET HADR RESUME;
After a few seconds/minutes depending on how long you have been out of sync, the dashboard now shows all green and we are back in sync.
To read more about resuming your availability groups, the documentation is always available.
Additional documentation: https://learn.microsoft.com/en-us/sql/t-sql/statements/alter-database-transact-sql-set-hadr?view=sql-server-ver16
Jim Salasek's SQL Server Blog 