SQL Monitor 6

Within the Availability replicas section of the Availability group overview, the State and Failover columns show:

the state, commit mode, and failover mode for all availability replicas
the state and failover information for all availability databases

Availability replicas

State, commit mode, and failover mode

The states in the table below are listed in order of severity, with the most severe first.

State	Explanation
Not joined	At least one database in the replica is not configured to be part of the availability group on this replica, but is joined on the other replicas.
Not connected	The secondary replica isn't connected to the primary replica.
Failed	A read failure has occurred during an attempt to retrieve information from the WSFC cluster.
Resolving	When, during a failover, the replica is not yet primary or secondary, it is said to be in the resolving state.
Not synchronizing*	Something is stopping the replica from synchronizing (asynchronous replicas only). For example, the availability group exists but the database is not yet restored on the secondary replica.
Synchronizing*	The availability replica is catching up with the primary replica.
Synchronized*	Everything’s up-to-date. If the commit mode is asynchronous, this only applies to primary replicas. If the commit mode is synchronous, this can apply to primary or secondary replicas.
For these three states, the state shown for the replica reflects the state of whichever of its databases is in the most serious condition. For example, if a replica contains two databases whose states are Synchronizing* and Not synchronizing, the replica shows Not synchronizing as its state.
Commit mode	Explanation
Synchronous	In synchronous-commit mode, the primary replica doesn't commit any transactions until it receives acknowledgement that all synchronous secondary replicas have finished hardening the commit in their log. This means no data will be lost on failover, because the primary and secondary replica databases are synchronized. However, the synchronous replication process causes a certain amount of transaction latency. This depends on factors such as the size of the rate of log growth, the send queue, and the rate at which log records are sent and received.
Asynchronous	In asynchronous-commit mode, the primary replica commits transactions without waiting for acknowledgement that the asynchronous-commit secondary replicas have hardened the log. This means there's no latency during the commit process. However, there could be data loss on failover, depending on how far the secondary is behind the primary at the time of the failover.
Primary	The primary replica has "primary" in parentheses, instead of "synchronous" or "asynchronous".

Failover mode	Explanation
Automatic	Automatic failover is initiated automatically in response to a failure. For automatic failover to work, the commit mode must be synchronous and the target replica must be synchronized.
Manual	Manual failover must be initiated by an administrator. For manual failover to work, the target replica must be synchronized.

Availability databases

State and failover information