--- title: "Configure distributed availability group (Always On Availability Group) | Microsoft Docs" ms.custom: "" ms.date: "08/17/2017" ms.prod: "sql-server-2016" ms.reviewer: "" ms.suite: "" ms.technology: "dbe-high-availability" ms.tgt_pltfrm: "" ms.topic: "article" ms.assetid: f7c7acc5-a350-4a17-95e1-e689c78a0900 caps.latest.revision: 28 author: "MikeRayMSFT" ms.author: "mikeray" manager: "jhubbard" --- # Configure distributed availability group To create a distributed availability group, you must create an availability group and listener on each Windows Server Failover Cluster (WSFC). You then combine these availability groups into a distributed availability group. The following steps provide a basic example in Transact-SQL. This example does not cover all of the details of creating availability groups and listeners; instead, it focuses on highlighting the key requirements. For a technical overview of distributed availability groups, see [Distributed availability groups](distributed-availability-groups.md). ## Prerequisites ### Set the endpoint listeners to listen to all IP addresses Make sure the endpoints can communicate between the different availability groups in the distributed availability group. If one availability group is set to a specific network on the endpoint, the distributed availability group does not work properly. On each server that hosts a replica in the distributed availability group, configure the listener to `LISTENER_IP = ALL`. #### Create a listener to listen to all IP addresses For example, the following script creates a listener endpoint on TCP port 5022 that listens on all IP addresses. ```sql CREATE ENDPOINT [aodns-hadr] STATE=STARTED AS TCP (LISTENER_PORT = 5022, LISTENER_IP = ALL) FOR DATA_MIRRORING ( ROLE = ALL, AUTHENTICATION = WINDOWS NEGOTIATE, ENCRYPTION = REQUIRED ALGORITHM AES ) GO ``` #### Alter a listener to listen to all IP addresses For example, the following script changes a listener endpoint to listen on all IP addresses. ```sql ALTER ENDPOINT [aodns-hadr] AS TCP (LISTENER_IP = ALL) GO ``` ## Create first availability group ### Create the primary availability group on the first cluster Create an availability group on the first WSFC. In this example, the availability group is named `ag1` for the database `db1`. ```sql CREATE AVAILABILITY GROUP [ag1] FOR DATABASE db1 REPLICA ON N'server1' WITH (ENDPOINT_URL = N'TCP://server1.contoso.com:5022', FAILOVER_MODE = AUTOMATIC, AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, BACKUP_PRIORITY = 50, SECONDARY_ROLE(ALLOW_CONNECTIONS = NO), SEEDING_MODE = AUTOMATIC), N'server2' WITH (ENDPOINT_URL = N'TCP://server2.contoso.com:5022', FAILOVER_MODE = AUTOMATIC, AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, BACKUP_PRIORITY = 50, SECONDARY_ROLE(ALLOW_CONNECTIONS = NO), SEEDING_MODE = AUTOMATIC); GO ``` >[!NOTE] >The preceding example uses direct seeding, where **SEEDING_MODE** is set to **AUTOMATIC** for both the replicas and the distributed availability group. This configuration sets the secondary replicas and secondary availability group to be automatically populated without requiring a manual backup and restore of primary database. ### Join the secondary replicas to the primary availability group Any secondary replicas must be joined to the availability group with **ALTER AVAILABILITY GROUP** with the **JOIN** option. Because direct seeding is used in this example, you must also call **ALTER AVAILABILITY GROUP** with the **GRANT CREATE ANY DATABASE** option. This setting allows the availability group to create the database and begin seeding it automatically from the primary replica. In this example, the following commands are run on the secondary replica, `server2`, to join the `ag1` availability group. The availability group is then permitted to create databases on the secondary. ```sql ALTER AVAILABILITY GROUP [ag1] JOIN ALTER AVAILABILITY GROUP [ag1] GRANT CREATE ANY DATABASE GO ``` >[!NOTE] >When the availability group creates a database on a secondary replica, it sets the database owner as the account that ran the `ALTER AVAILABILITY GROUP` statement to grant permission to create any database. For complete information, see [Grant create database permission on secondary replica to availability group](automatic-seeding-secondary-replicas.md#grantCreate). ### Create a listener for the primary availability group Next add a listener for the primary availability group on the first WSFC. In this example, the listener is named `ag1-listener`. For detailed instructions on creating a listener, see [Create or Configure an Availability Group Listener (SQL Server)](../../../database-engine/availability-groups/windows/create-or-configure-an-availability-group-listener-sql-server.md). ```sql ALTER AVAILABILITY GROUP [ag1]     ADD LISTENER 'ag1-listener' ( WITH IP ( ('2001:db88:f0:f00f::cf3c'),('2001:4898:e0:f213::4ce2') ) , PORT = 60173); GO ``` ## Create second availability group Then on the second WSFC, create a second availability group, `ag2`. In this case, the database is not specified, because it is automatically seeded from the primary availability group. ```sql CREATE AVAILABILITY GROUP [ag2] FOR REPLICA ON N'server3' WITH (ENDPOINT_URL = N'TCP://server3.contoso.com:5022', FAILOVER_MODE = MANUAL, AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, BACKUP_PRIORITY = 50, SECONDARY_ROLE(ALLOW_CONNECTIONS = NO), SEEDING_MODE = AUTOMATIC), N'server4' WITH (ENDPOINT_URL = N'TCP://server4.contoso.com:5022', FAILOVER_MODE = MANUAL, AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, BACKUP_PRIORITY = 50, SECONDARY_ROLE(ALLOW_CONNECTIONS = NO), SEEDING_MODE = AUTOMATIC); GO ``` > [!NOTE] > The secondary availability group must use the same database mirroring endpoint (in this example port 5022). Otherwise, replication will stop after a local failover. ### Join the secondary replicas to the secondary availability group In this example, the following commands are run on the secondary replica, `server4`, to join the `ag2` availability group. The availability group is then permitted to create databases on the secondary to support direct seeding. ```sql ALTER AVAILABILITY GROUP [ag2] JOIN ALTER AVAILABILITY GROUP [ag2] GRANT CREATE ANY DATABASE GO ``` ### Create a listener for the secondary availability group Next add a listener for the secondary availability group on the second WSFC. In this example, the listener is named `ag2-listener`. For detailed instructions on creating a listener, see [Create or Configure an Availability Group Listener (SQL Server)](../../../database-engine/availability-groups/windows/create-or-configure-an-availability-group-listener-sql-server.md). ``` ALTER AVAILABILITY GROUP [ag2]     ADD LISTENER 'ag2-listener' ( WITH IP ( ('2001:db88:f0:f00f::cf3c'),('2001:4898:e0:f213::4ce2') ) , PORT = 60173); GO ``` ## Create distributed availability group on first cluster On the first WSFC, create a distributed availability group (named `distributedag` in this example). Use the **CREATE AVAILABILITY GROUP** command with the **DISTRIBUTED** option. The **AVAILABILITY GROUP ON** parameter specifies the member availability groups `ag1` and `ag2`. ```sql CREATE AVAILABILITY GROUP [distributedag]    WITH (DISTRIBUTED)    AVAILABILITY GROUP ON       'ag1' WITH    (          LISTENER_URL = 'tcp://ag1-listener.contoso.com:5022',          AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT,          FAILOVER_MODE = MANUAL,          SEEDING_MODE = AUTOMATIC       ),       'ag2' WITH       (          LISTENER_URL = 'tcp://ag2-listener.contoso.com:5022',          AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT,          FAILOVER_MODE = MANUAL,          SEEDING_MODE = AUTOMATIC       ); GO ``` > [!NOTE] > The **LISTENER_URL** specifies the listener for each availability group along with the database mirroring endpoint of the availability group. In this example, that is port `5022` (not port `60173` used to create the listener). ## Join distributed availability group on second cluster Then join the distributed availability group on the second WSFC. ```sql ALTER AVAILABILITY GROUP [distributedag]    JOIN    AVAILABILITY GROUP ON       'ag1' WITH    (          LISTENER_URL = 'tcp://ag1-listener.contoso.com:5022',          AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT,          FAILOVER_MODE = MANUAL,          SEEDING_MODE = AUTOMATIC       ),       'ag2' WITH       (          LISTENER_URL = 'tcp://ag2-listener.contoso.com:5022',          AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT,          FAILOVER_MODE = MANUAL,          SEEDING_MODE = AUTOMATIC       ); GO ``` ## Fail over to a secondary availability group Only manual failover is supported at this time. The following Transact-SQL statement fails over the distributed availability group named `distributedag`: 1. Set the availability mode to synchronous commit for the secondary availability group. ```sql ALTER AVAILABILITY GROUP [distributedag] MODIFY AVAILABILITY GROUP ON 'ag1' WITH ( LISTENER_URL = 'tcp://ag1-listener.contoso.com:5022', AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT, FAILOVER_MODE = MANUAL, SEEDING_MODE = MANUAL ), 'ag2' WITH ( LISTENER_URL = 'tcp://ag2-listener.contoso.com:5022', AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, FAILOVER_MODE = MANUAL, SEEDING_MODE = MANUAL ); ``` 1. Wait until the status of the distributed availability group has changed to `SYNCHRONIZED`. Run the following query on the SQL Server that hosts the primary replica of the primary availability group. ```sql SELECT ag.name , drs.database_id , drs.group_id , drs.replica_id , drs.synchronization_state_desc , drs.end_of_log_lsn FROM sys.dm_hadr_database_replica_states drs, sys.availability_groups ag WHERE drs.group_id = ag.group_id; ``` Proceed after the availability group **synchronization_state_desc** is `SYNCHRONIZED`. If **synchronization_state_desc** is not `SYNCHRONIZED`, run the command every five seconds until it changes. Do not proceed until the **synchronization_state_desc** = `SYNCHRONIZED`. 1. On the SQL Server that hosts the primary replica for the primary availability group, set the distributed availability group role to `SECONDARY`. ```sql ALTER AVAILABILITY GROUP distributedag SET (ROLE = SECONDARY); ``` At this point, the distributed availability group is not available. 1. Test the failover readiness. Run the following query: ```sql SELECT ag.name, drs.database_id, drs.group_id, drs.replica_id, drs.synchronization_state_desc, drs.end_of_log_lsn FROM sys.dm_hadr_database_replica_states drs, sys.availability_groups ag WHERE drs.group_id = ag.group_id; ``` The availability group is ready to fail over when the **synchronization_state_desc** is `SYNCHRONIZED` and the **end_of_log_lsn** is the same for both availability groups. 1. Fail over from the primary availability group to the secondary availability group. Run the following command on the SQL Server that hosts the primary replica for the secondary availability group. ```sql ALTER AVAILABILITY GROUP distributedag FORCE_FAILOVER_ALLOW_DATA_LOSS; ``` After this step, the distributed availability group is available. After completing the steps above, the distributed availability group fails over without any data loss. If the availability groups are across a geographical distance that causes latency, change the availability mode back to ASYNCHRONOUS_COMMIT. ## Remove a distributed availability group The following Transact-SQL statement removes a distributed availability group named `distributedag`: ```sql DROP AVAILABILITY GROUP [distributedag] ``` ## Create distributed availability group on failover cluster instances You can create a distributed availability group using an availability group on a failover cluster instance (FCI). In this case, you don't need an availability group listener. Use the virtual network name (VNN) for the primary replica of the FCI instance. The following example shows a distributed availability group called SQLFCIDAG. One availability group is SQLFCIAG. SQLFCIAG has two FCI replicas. The VNN for the primary FCI replica is SQLFCIAG-1, and the VNN for the secondary FCI replica is SQLFCIAG-2. The distributed availability group also includes SQLAG-DR, for disaster recovery. ![Always On Availability Group Distributed](../../../database-engine/availability-groups/windows/media/always-on-availability-group-distributed.png) The following DDL creates this distributed availability group. ```sql CREATE AVAILABILITY GROUP [SQLFCIDAG] WITH (DISTRIBUTED) AVAILABILITY GROUP ON 'SQLFCIAG' WITH ( LISTENER_URL = 'tcp://SQLFCIAG-1.contoso.com:5022', AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT, FAILOVER_MODE = MANUAL, SEEDING_MODE = AUTOMATIC ), 'SQLAG-DR' WITH ( LISTENER_URL = 'tcp://SQLAG-DR.contoso.com:5022', AVAILABILITY_MODE = ASYNCHRONOUS_COMMIT, FAILOVER_MODE = MANUAL, SEEDING_MODE = AUTOMATIC ); ``` The listener URL is the VNN of the primary FCI instance. ## Manually fail over FCI in distributed availability group To manually fail over the FCI availability group, update the distributed availability group to reflect the change of listener URL. For example, run the following DDL on both the primary AG and the secondary AG of SQLFCIAG: ```sql ALTER AVAILABILITY GROUP [SQLFCIDAG] MODIFY AVAILABILITY GROUP ON 'SQLFCIAG' WITH ( LISTENER_URL = 'tcp://SQLFCIAG-2.contoso.com:5022' ) ``` ## Next steps [CREATE AVAILABILITY GROUP (Transact-SQL)](../../../t-sql/statements/create-availability-group-transact-sql.md) [ALTER AVAILABILITY GROUP (Transact-SQL)](../../../t-sql/statements/alter-availability-group-transact-sql.md)