Always ON Query's

SQL instance is part of Availability Groups details:

SELECT
AG.name AS [AG_Group_Name],
ISNULL(agstates.primary_replica, '') AS [PrimaryReplicaServerName],
ISNULL(arstates.role, 3) AS [LocalReplicaRole]
FROM master.sys.availability_groups AS AG
LEFT OUTER JOIN master.sys.dm_hadr_availability_group_states as agstates
    ON AG.group_id = agstates.group_id
INNER JOIN master.sys.availability_replicas AS AR
    ON AG.group_id = AR.group_id
INNER JOIN master.sys.dm_hadr_availability_replica_states AS arstates
    ON AR.replica_id = arstates.replica_id AND arstates.is_local = 1
ORDER BY [Name] ASC


To get some information about the databases in the Availability Group:

SELECT
AG.name AS [AvailabilityGroupName],
ISNULL(agstates.primary_replica, '') AS [PrimaryReplicaServerName],
ISNULL(arstates.role, 3) AS [LocalReplicaRole],
dbcs.database_name AS [DatabaseName],
ISNULL(dbrs.synchronization_state, 0) AS [SynchronizationState],
ISNULL(dbrs.is_suspended, 0) AS [IsSuspended],
ISNULL(dbcs.is_database_joined, 0) AS [IsJoined]
FROM master.sys.availability_groups AS AG
LEFT OUTER JOIN master.sys.dm_hadr_availability_group_states as agstates
   ON AG.group_id = agstates.group_id
INNER JOIN master.sys.availability_replicas AS AR
   ON AG.group_id = AR.group_id
INNER JOIN master.sys.dm_hadr_availability_replica_states AS arstates
   ON AR.replica_id = arstates.replica_id AND arstates.is_local = 1
INNER JOIN master.sys.dm_hadr_database_replica_cluster_states AS dbcs
   ON arstates.replica_id = dbcs.replica_id
LEFT OUTER JOIN master.sys.dm_hadr_database_replica_states AS dbrs
   ON dbcs.replica_id = dbrs.replica_id AND dbcs.group_database_id = dbrs.group_database_id
ORDER BY AG.name ASC, dbcs.database_name

List of databases that are secondary in the Availability Group,  to be excluded when writes are required:

SELECT DISTINCT
dbcs.database_name AS [DatabaseName]
FROM master.sys.availability_groups AS AG
LEFT OUTER JOIN master.sys.dm_hadr_availability_group_states as agstates
   ON AG.group_id = agstates.group_id
INNER JOIN master.sys.availability_replicas AS AR
   ON AG.group_id = AR.group_id
INNER JOIN master.sys.dm_hadr_availability_replica_states AS arstates
   ON AR.replica_id = arstates.replica_id AND arstates.is_local = 1
INNER JOIN master.sys.dm_hadr_database_replica_cluster_states AS dbcs
   ON arstates.replica_id = dbcs.replica_id
LEFT OUTER JOIN master.sys.dm_hadr_database_replica_states AS dbrs
   ON dbcs.replica_id = dbrs.replica_id AND dbcs.group_database_id = dbrs.group_database_id
WHERE ISNULL(arstates.role, 3) = 2 AND ISNULL(dbcs.is_database_joined, 0) = 1
ORDER BY  dbcs.database_name

Monitoring AGs in WSFC Cluster:

select * from sys.dm_hadr_cluster

select * from sys.dm_hadr_cluster_members

select * from sys.dm_hadr_cluster_networks

select * from sys.dm_hadr_instance_node_map

select * from sys.dm_hadr_name_id_map

Monitoring AGs:

select * from sys.availability_groups

select * from sys.availability_groups_cluster

select * from sys.dm_hadr_availability_group_states

monitoring availability replicas

select * from sys.availability_replicas

select * from sys.availability_read_only_routing_lists

select * from sys.dm_hadr_availability_replica_cluster_nodes

select * from sys.dm_hadr_availability_replica_cluster_states

select * from sys.dm_hadr_availability_replica_states

select  sys.fn_hadr_backup_is_preferred_replica ('DBNAME') -- Used to determine if the current replica is the preferred backup replica.

Monitoring Availability databases :

select * from sys.availability_databases_cluster

select * from sys.databases

select * from sys.dm_hadr_auto_page_repair

select * from sys.dm_hadr_database_replica_states

select * from sys.dm_hadr_database_replica_cluster_states

Monitor the availability group listeners:

select * from sys.availability_group_listener_ip_addresses

select * from sys.availability_group_listeners

select * from sys.dm_tcp_listener_states

Please refer the below queries for AlwaysOn Availability Groups monitoring reference:

    SERVERPROPERTY (Transact-SQL)

    sys.availability_group_listener_ip_addresses (Transact-SQL)

    sys.availability_group_listeners (Transact-SQL)

    sys.availability_databases_cluster (Transact-SQL)

    sys.availability_groups (Transact-SQL)

    sys.availability_read_only_routing_lists (Transact-SQL)

    sys.availability_replicas (Transact-SQL)

    sys.dm_hadr_availability_replica_cluster_nodes (Transact-SQL)

    sys.dm_hadr_availability_replica_cluster_states (Transact-SQL)

    sys.database_mirroring_endpoints (Transact-SQL)

    sys.dm_hadr_auto_page_repair (Transact-SQL)

    sys.dm_hadr_availability_group_states (Transact-SQL)

    sys.dm_hadr_availability_replica_cluster_states (Transact-SQL)

    sys.dm_hadr_availability_replica_states (Transact-SQL)

    sys.dm_hadr_database_replica_states (Transact-SQL)

    sys.dm_hadr_database_replica_cluster_states (Transact-SQL)

    sys.dm_hadr_cluster (Transact-SQL)

    sys.dm_hadr_cluster_members (Transact-SQL)

    sys.dm_hadr_cluster_networks (Transact-SQL)

    sys.dm_hadr_database_replica_cluster_states (Transact-SQL)

    sys.dm_hadr_database_replica_states (Transact-SQL)

    sys.dm_hadr_instance_node_map (Transact-SQL)

    sys.dm_hadr_name_id_map (Transact-SQL)

    sys.dm_os_performance_counters (Transact-SQL)

    sys.dm_tcp_listener_states (Transact-SQL)

    sys.fn_hadr_backup_is_preferred_replica (Transact-SQL)


Thanks To: RAJU RASAGOUNDER NZ