Configure Replication for Always On Availability Groups (SQL Server)
THIS TOPIC APPLIES TO: SQL Server (starting with 2016)Azure SQL DatabaseAzure SQL Data Warehouse Parallel Data Warehouse
Configuring SQL Server replication and Always On availability groups involves seven steps. Each step is described in more detail in the following sections.
Steps 1 and 2 can be performed in either order.
1. Configure the Database Publications and Subscriptions
Configure the distributor
The distribution database cannot be placed in an availability group.
Configure distribution at the distributor. If stored procedures are being used for configuration, run sp_adddistributor. Use the @password parameter to identify the password that will be used when a remote publisher connects to the distributor. The password will also be needed at each remote publisher when the remote distributor is set up.
USE master; GO EXEC sys.sp_adddistributor @distributor = 'MyDistributor', @password = '**Strong password for distributor**';
Create the distribution database at the distributor. If stored procedures are being used for configuration, run sp_adddistributiondb.
USE master; GO EXEC sys.sp_adddistributiondb @database = 'distribution', @security_mode = 1;
Configure the remote publisher. If stored procedures are being used to configure the distributor, run sp_adddistpublisher. The @security_mode parameter is used to determine how the publisher validation stored procedure that is run from the replication agents, connects to the current primary. If set to 1 Windows authentication is used to connect to the current primary. If set to 0, SQL Server authentication is used with the specified @login and @password values. The login and password specified must be valid at each secondary replica for the validation stored procedure to successfully connect to that replica.
If any modified replication agents run on a computer other than the distributor, use of Windows authentication for the connection to the primary will require Kerberos authentication to be configured for the communication between the replica host computers. Use of a SQL Server login for the connection to the current primary will not require Kerberos authentication.
USE master; GO EXEC sys.sp_adddistpublisher @publisher = 'AGPrimaryReplicaHost', @distribution_db = 'distribution', @working_directory = '\\MyReplShare\WorkingDir', @login = 'MyPubLogin', @password = '**Strong password for publisher**';
For more information, see sp_adddistpublisher (Transact-SQL).
Configure the publisher at the original publisher
Configure remote distribution. If stored procedures are being used to configure the publisher, run sp_adddistributor. Specify the same value for @password as that used when sp_adddistrbutor was run at the distributor to set up distribution.
exec sys.sp_adddistributor @distributor = 'MyDistributor', @password = 'MyDistPass'
Enable the database for replication. If stored procedures are being used to configure the publisher, run sp_replicationdboption. If both transactional and merge replication are to be configured for the database, each must be enabled.
USE master; GO EXEC sys.sp_replicationdboption @dbname = 'MyDBName', @optname = 'publish', @value = 'true'; EXEC sys.sp_replicationdboption @dbname = 'MyDBName', @optname = 'merge publish', @value = 'true';
Create the replication publication, articles, and subscriptions. For more information about how to configure replication, see Publishing Data and Database objects.
2. Configure the Always On Availability Group
At the intended primary, create the availability group with the published (or to be published) database as a member database. If using the Availability Group Wizard, you can either allow the wizard to initially synchronize the secondary replica databases or you can perform the initialization manually by using backup and restore.
Create a DNS listener for the availability group that will be used by the replication agents to connect to the current primary. The listener name that is specified will be used as the target of redirection for the original publisher/published database pair. For example, if you are using DDL to configure the availability group, the following code example can be used to specify an availability group listener for an existing availability group named
ALTER AVAILABILITY GROUP 'MyAG' ADD LISTENER 'MyAGListenerName' (WITH IP (('10.120.19.155', '255.255.254.0')));
For more information, see Creation and Configuration of Availability Groups (SQL Server).
3. Insure that all of the Secondary Replica Hosts are Configured for Replication
At each secondary replica host, verify that SQL Server has been configured to support replication. The following query can be run at each secondary replica host to determine whether replication is installed:
USE master; GO DECLARE @installed int; EXEC @installed = sys.sp_MS_replication_installed; SELECT @installed;
If @installed is 0, replication must be added to the SQL Server installation.
4. Configure the Secondary Replica Hosts as Replication Publishers
A secondary replica cannot act as a replication publisher or republisher but replication must be configured so that the secondary can take over after a failover. At the distributor, configure distribution for each secondary replica host. Specify the same distribution database and working directory as was specified when the original publisher was added to the distributor. If you are using stored procedures to configure distribution, use sp_adddistpublisher to associate the remote publishers with the distributor. If @login and @password were used for the original publisher, specify the same values for each when you add the secondary replica hosts as publishers.
EXEC sys.sp_adddistpublisher @publisher = 'AGSecondaryReplicaHost', @distribution_db = 'distribution', @working_directory = '\\MyReplShare\WorkingDir', @login = 'MyPubLogin', @password = '**Strong password for publisher**';
At each secondary replica host, configure distribution. Identify the distributor of the original publisher as the remote distributor. Use the same password as that used when sp_adddistributor was run originally at the distributor. If stored procedures are being used to configure distribution, the @password parameter of sp_adddistributor is used to specify the password.
EXEC sp_adddistributor @distributor = 'MyDistributor', @password = '**Strong password for distributor**';
At each secondary replica host, make sure that the push subscribers of the database publications appear as linked servers. If stored procedures are being used to configure the remote publishers, use sp_addlinkedserver to add the subscribers (if not already present) as linked servers to the publishers.
EXEC sys.sp_addlinkedserver @server = 'MySubscriber';
5. Redirect the Original Publisher to the AG Listener Name
At the distributor, in the distribution database, run the stored procedure sp_redirect_publisher to associate the original publisher and the published database with the availability group listener name of the availability group.
USE distribution; GO EXEC sys.sp_redirect_publisher @original_publisher = 'MyPublisher', @publisher_db = 'MyPublishedDB', @redirected_publisher = 'MyAGListenerName';
6. Run the Replication Validation Stored Procedure to Verify the Configuration
At the distributor, in the distribution database, run the stored procedure sp_validate_replica_hosts_as_publishers to verify that all replica hosts are now configured to serve as publishers for the published database.
USE distribution; GO DECLARE @redirected_publisher sysname; EXEC sys.sp_validate_replica_hosts_as_publishers @original_publisher = 'MyPublisher', @publisher_db = 'MyPublishedDB', @redirected_publisher = @redirected_publisher output;
The stored procedure sp_validate_replica_hosts_as_publishers should be run from a login with sufficient authorization at each availability group replica host to query for information about the availability group. Unlike sp_validate_redirected_publisher, it uses the credentials of the caller and does not use the login retained in msdb.dbo.MSdistpublishers to connect to the availability group replicas.
sp_validate_replica_hosts_as_publishers will fail with the following error when validating secondary replica hosts that do not allow read access, or require read intent to be specified.
Msg 21899, Level 11, State 1, Procedure sp_hadr_verify_subscribers_at_publisher, Line 109
The query at the redirected publisher 'MyReplicaHostName' to determine whether there were sysserver entries for the subscribers of the original publisher 'MyOriginalPublisher' failed with error '976', error message 'Error 976, Level 14, State 1, Message: The target database, 'MyPublishedDB', is participating in an availability group and is currently not accessible for queries. Either data movement is suspended or the availability replica is not enabled for read access. To allow read-only access to this and other databases in the availability group, enable read access to one or more secondary availability replicas in the group. For more information, see the ALTER AVAILABILITY GROUP statement in SQL Server Books Online.'.
One or more publisher validation errors were encountered for replica host 'MyReplicaHostName'.
This is expected behavior. You must verify the presence of the subscriber server entries at these secondary replica hosts by querying for the sysserver entries directly at the host.
7. Add the Original Publisher to Replication Monitor
At each availability group replica, add the original publisher to Replication Monitor.
To create and configure an availability group
Prerequisites, Restrictions, and Recommendations for Always On Availability Groups (SQL Server)
Overview of Always On Availability Groups (SQL Server)
Always On Availability Groups: Interoperability (SQL Server)
SQL Server Replication