- 7 minutes to read
Applies to: SQL Server
This topic describes how to perform a manual failover without data loss (a planned manual failover) on an Always On availability group by using SQL Server Management Studio, Transact-SQL, or PowerShell in SQL Server. An availability group fails over at the level of an availability replica. A planned manual failover, like any Always On availability group failover, transitions a secondary replica to primary role. Concurrently, the failover transitions the former primary replica to the secondary role.
A planned manual failover is supported only when the primary replica and the target secondary replica are running in synchronous-commit mode and are currently synchronized. A planned manual failover preserves all the data in the secondary databases that are joined to the availability group on the target secondary replica. After the former primary replica transitions to the secondary role, its databases become secondary databases. Then they begin to synchronize with the new primary databases. After they all transition into the SYNCHRONIZED state, the new secondary replica becomes eligible to serve as the target of a future planned manual failover.
If the secondary and primary replicas are both configured for automatic failover mode, after the secondary replica is synchronized, it also can serve as the target for an automatic failover. For more information, see Availability modes (Always On availability groups).
Before you begin
There are specific procedures to fail over a read-scale availability group with no cluster manager. When an availability group has CLUSTER_TYPE = NONE, follow the procedures under Fail over the primary replica on a read-scale availability group.
Limitations and restrictions
A failover command returns as soon as the target secondary replica has accepted the command. However, database recovery occurs asynchronously after the availability group has finished failing over.
Cross-database consistency across databases within the availability group might not be maintained on failover.
Note(Video) SQL Server Always On Series - Always On Planned Manual Failover #jbswiki #alwayson
Support for cross-database and distributed transactions vary by SQL Server and operating system versions. For more information, see Cross-database transactions and distributed transactions for Always On availability groups and database mirroring (SQL Server).
Prerequisites and restrictions
Both the target secondary replica and the primary replica must be running in synchronous-commit availability mode.
Currently, the target secondary replica must be synchronized with the primary replica. All the secondary databases on this secondary replica must be joined to the availability group. They also must be synchronized with their corresponding primary databases (that is, the local secondary databases must be SYNCHRONIZED).See AlsoPerform operations on data - Azure Logic AppsPerform inner joins (LINQ in C#)Get started with formulas in canvas apps - Power AppsReview access to groups & applications in access reviews - Microsoft Entra
To determine the failover readiness of a secondary replica, query the is_failover_ready column in the sys.dm_hadr_database_replica_cluster_states dynamic management view. Or you can look at the Failover Readiness column of the Always On group dashboard.
This task is supported only on the target secondary replica. You must be connected to the server instance that hosts the target secondary replica.
The ALTER AVAILABILITY GROUP permission is required on the availability group. The CONTROL AVAILABILITY GROUP permission, the ALTER ANY AVAILABILITY GROUP permission, or the CONTROL SERVER permission also is required.
Use SQL Server Management Studio
To manually fail over an availability group:
In Object Explorer, connect to a server instance that hosts a secondary replica of the availability group that needs to be failed over. Expand the server tree.
Expand the Always On High Availability node and the Availability Groups node.
Right-click the availability group to be failed over, and select Failover.
The Failover Availability Group wizard starts. For more information, see Use the Failover Availability Group wizard (SQL Server Management Studio).
To manually fail over an availability group:
Connect to the server instance that hosts the target secondary replica.(Video) How to Manually Failover an AlwaysOn Availability Group | XTIVIA Video Blog
Use the ALTER AVAILABILITY GROUP statement, as follows:
ALTER AVAILABILITY GROUP group_name FAILOVER
In the statement, group_name is the name of the availability group.
The following example manually fails over the MyAg availability group to the connected secondary replica:
ALTER AVAILABILITY GROUP MyAg FAILOVER;
To manually fail over an availability group:
Change the directory (cd) to the server instance that hosts the target secondary replica.
Use the Switch-SqlAvailabilityGroup cmdlet.
To view the syntax of a cmdlet, use the Get-Help cmdlet in the SQL Server PowerShell environment. For more information, see Get help for SQL Server PowerShell.
The following example manually fails over the MyAg availability group to the secondary replica with the specified path:
Switch-SqlAvailabilityGroup -Path SQLSERVER:\Sql\SecondaryServer\InstanceName\AvailabilityGroups\MyAg
To set up and use the SQL Server PowerShell provider:
- SQL Server PowerShell provider
- Get help for SQL Server PowerShell
Follow up: After you manually fail over an availability group
If you failed over outside the automatic failover set of the availability group, adjust the quorum votes of the Windows Server failover clustering nodes to reflect your new availability group configuration. For more information, see Windows Server failover clustering (WSFC) with SQL Server.
Fail over the primary replica on a read-scale availability group
Each availability group has only one primary replica. The primary replica allows reads and writes. To change which replica is primary, you can fail over. In a typical availability group, the cluster manager automates the failover process. In an availability group with cluster type NONE, the failover process is manual.
There are two ways to fail over the primary replica in an availability group with cluster type NONE:
- Manual failover without data loss
- Forced manual failover with data loss
Manual failover without data loss
Use this method when the primary replica is available, but you need to temporarily or permanently change which instance hosts the primary replica.To avoid potential data loss, before you issue the manual failover, ensure that the target secondary replica is up to date.
To manually fail over without data loss:
Make the current primary and target secondary replica
ALTER AVAILABILITY GROUP [AGRScale] MODIFY REPLICA ON N'<node2>' WITH (AVAILABILITY_MODE = SYNCHRONOUS_COMMIT);
To identify that active transactions are committed to the primary replica and at least one synchronous secondary replica, run the following query:
SELECT ag.name, drs.database_id, drs.group_id, drs.replica_id, drs.synchronization_state_desc, ag.sequence_numberFROM sys.dm_hadr_database_replica_states drs, sys.availability_groups agWHERE drs.group_id = ag.group_id;
The secondary replica is synchronized when
The following script sets
REQUIRED_SYNCHRONIZED_SECONDARIES_TO_COMMITto 1 on an availability group named
ag1. Before you run the following script, replace
ag1with the name of your availability group:
ALTER AVAILABILITY GROUP [AGRScale] SET (REQUIRED_SYNCHRONIZED_SECONDARIES_TO_COMMIT = 1);
This setting ensures that every active transaction is committed to the primary replica and at least one synchronous secondary replica.
This setting is not specific to failover and should be set based on the requirements of the environment.
Set the primary replica and the secondary replica(s) not participating in the failover offline to prepare for the role change:
ALTER AVAILABILITY GROUP [AGRScale] OFFLINE
Promote the target secondary replica to primary.
ALTER AVAILABILITY GROUP AGRScale FORCE_FAILOVER_ALLOW_DATA_LOSS;
Update the role of the old primary and other secondaries to
SECONDARY, run the following command on the SQL Server instance that hosts the old primary replica:
ALTER AVAILABILITY GROUP [AGRScale] SET (ROLE = SECONDARY);
To delete an availability group, use DROP AVAILABILITY GROUP. For an availability group that's created with cluster type NONE or EXTERNAL, execute the command on all replicas that are part of the availability group.(Video) SQL Server Always On Series - Always On Availability Group Automatic Failover to a Particular Node
Resume data movement, run the following command for every database in the availability group on the SQL Server instance that hosts the primary replica:
ALTER DATABASE [db1] SET HADR RESUME
Re-create any listener you created for read-scale purposes and that isn't managed by a cluster manager. If the original listener points to the old primary, drop it and re-create it to point to the new primary.
Forced manual failover with data loss
If the primary replica is not available and can't immediately be recovered, then you need to force a failover to the secondary replica with data loss. However, if the original primary replica recovers after failover, it will assume the primary role. To avoid having each replica be in a different state, remove the original primary from the availability group after a forced failover with data loss. Once the original primary comes back online, remove the availability group from it entirely.
To force a manual failover with data loss from primary replica N1 to secondary replica N2, follow these steps:
On the secondary replica (N2), initiate the forced failover:
ALTER AVAILABILITY GROUP [AGRScale] FORCE_FAILOVER_ALLOW_DATA_LOSS;
On the new primary replica (N2), remove the original primary (N1):
ALTER AVAILABILITY GROUP [AGRScale]REMOVE REPLICA ON N'N1';
Validate that all application traffic is pointed to the listener and/or the new primary replica.
If the original primary (N1) comes online, immediately take availability group AGRScale offline on the original primary (N1):
ALTER AVAILABILITY GROUP [AGRScale] OFFLINE
If there is data or unsynchronized changes, preserve this data via backups or other data replicating options that suit your business needs.
Next, remove the availability group from the original primary (N1):
DROP AVAILABILITY GROUP [AGRScale];
Drop the availability group database on original primary replica (N1):
USE [master]GODROP DATABASE [AGDBRScale]GO
(Optional) If desired, you can now add N1 back as a new secondary replica to the availability group AGRScale.
- Overview of Always On availability groups (SQL Server)
- Failover and failover modes (Always On availability groups)
- Perform a forced manual failover of an availability group (SQL Server)
How do you always perform on failover? ›
Right-click on the availability group to failover from the primary instance and go to failover. Go through the failover wizard and perform an AG failover. Alternatively, you can run the Alter Availability Group command to initiate a failover from the primary to the secondary replica.How automatic failover happens in AlwaysOn availability groups? ›
Always On Availability Groups monitors the health of both replicas in an automatic failover set. If either replica fails, the availability group's health state is set to CRITICAL. If the secondary replica fails, automatic failover is not possible because the automatic failover target is unavailable.How do I manually failover an Azure SQL database? ›
In the Azure portal, browse to the primary database in the geo-replication partnership. Scroll to Data management, and then select Replicas. In the Geo replicas list, select the database you want to become the new primary, select the ellipsis, and then select Forced failover. Select Yes to begin the failover.What is the difference between AlwaysOn failover cluster instances and AlwaysOn availability groups? ›
An SQL AlwaysOn failover cluster instance provides high availability and disaster recovery at the SQL Server level. AlwaysOn Availability Groups (AAG) provide high availability and disaster recovery at SQL database level.How do I failover a SQL Server database? ›
- Connect to the principal server instance and, in the Object Explorer pane, click the server name to expand the server tree.
- Expand Databases, and select the database to be failed over.
- Right-click the database, select Tasks, and then click Mirror. ...
- Click Failover.
PFO allows you to keep your business running with minimal downtime even during planned downtimes and guarantees zero data loss.What is the difference between always on and high availability? ›
The Always On availability groups feature is a high-availability and disaster-recovery solution that provides an enterprise-level alternative to database mirroring. Introduced in SQL Server 2012 (11. x), Always On availability groups maximizes the availability of a set of user databases for an enterprise.How do I refresh a Alwayson availability group? ›
At a high level, it requires the following steps: Remove the database from the primary replica of SQL Server Always On Availability Group. Restore a database from the production database backup. Add the database back to the availability group using manual or automatic seeding.What is the difference between failover and high availability? ›
In high availability two firewalls are usually connected by a mirrored link. This link enables both firewall appliances to keep and maintain an identical state. A failover does not really occur because both firewalls are all ready in current state. The active firewall just takes on all the processing load.What are the issues with always on availability groups? ›
Typical configuration problems include Always On availability groups is disabled, accounts are incorrectly configured, the database mirroring endpoint doesn't exist, the endpoint is inaccessible (SQL Server Error 1418), network access doesn't exist, and a join database command fails (SQL Server Error 35250).
What is the disadvantage of always on SQL Server? ›
Disadvantages. You cannot safeguard system databases (Master, Model, and MSDB) from instance or database level failure. Always On does not support adding them to the availability groups. Always On does not synchronize SQL Server logins, linked servers, and Agent jobs to the secondary databases.How to create a failover group in SQL Server? ›
Select the name of the server under Server name to open the settings for the server. Select Failover groups under the Settings pane, and then select Add group to create a new failover group. On the Failover Group page, enter or select the required values, and then select Create.How does SQL Server failover work? ›
In the event of a failover, the WSFC service transfers ownership of instance's resources to a designated failover node. The SQL Server instance is then re-started on the failover node, and databases are recovered as usual. At any given moment, only a single node in the cluster can host the FCI and underlying resources.How do you set up a failover server? ›
- Select Configure Failover. Right-click the selected DHCP scope, and select Configure Failover from the context menu. ...
- Specify the partner server. ...
- Create new failover relationship. ...
- Select Finish to complete configuration.
All servers must use the same version of Windows Server 2016. All servers must be joined to an Active Directory domain. All servers must use identical hardware components.Whats the difference between a planned failover and the failover option when right clicking on the virtual machine and replica? ›
In the case of a “Planned Failover”, the Hyper-V Primary Server is notified of the operation/action so it takes necessary actions for the primary Virtual Machine. On the other hand, “Unplanned Failover”, which is performed at the Replica Server, does not provide any notification to the Replica Server.What is the difference between database mirroring and failover cluster in SQL? ›
Failover clusters provide high-availability support for an entire Microsoft SQL Server instance, in contrast to database mirroring, which provides high-availability support for a single database. Database mirroring works between failover clusters and, also, between a failover cluster and a nonclustered host.What is always on availability mode in SQL Server? ›
Always On SQL Server is a High Availability and Disaster Recovery solution introduced in SQL Server 2012. It increases the availability by providing a failover environment for Availability Databases that failover together.How long does SQL failover take? ›
Somewhere between 15 seconds and a minute usually. That said, there are a few reasons why failover may be on the slower side: Virtual Log File Count (VLFs)How do I restore a SQL Server database Alwayson availability group? ›
- Connect to Primary -> Go to Availabilty groups --> Availabilty Databases and Remove Secondary Database OR T-Sql. ...
- Take FULL Backup from Primary and Restore into Secondary. ...
- Take T-Log Backup from Primary and Restore into Secondary.
What is the difference between planned failover and failover? ›
Failover Now = Turns on the latest replica. workload from source VM is not migrated so we actually have some data loss depends on when the last replication was done. Planned Failover = Moves all workload in from source vm to replica. Powers off source vm and the replica is now acting same as the source VM.What is failover procedure? ›
What is failover? Failover is the process of switching to a redundant or standby computer server, system, hardware component or network. Other terms also used to describe this capability include role-swap or switching.What is failover and example? ›
Failover can apply to any aspect of a system. Within a personal computer, for example, failover might be a mechanism to protect against a failed processor. Within a network, failover can apply to any network component or system of components, such as a connection path, storage device or Web server.What are the 3 major principles to ensure high availability? ›
- Single points of failure. A single point of failure is a component that would cause the whole system to fail if it fails. ...
- Reliable crossover. Building redundancy into these systems is also important. ...
- Failure detectability.
- High availability through redundancy. An important strategy for maintaining high availability is having redundant components. ...
- High availability through failover. ...
- High availability through clustering. ...
- Database logging.
You can have more than one AlwaysOn Availability Group on your instance, but databases cannot belong to more than one group.What is always on failover cluster? ›
SQL Server Always On Failover Cluster Instances (FCIs) use Windows Server Failover Clustering (WSFC) to provide high availability at the server instance level. An FCI is a single instance of SQL Server that is installed across WSFC nodes to provide high availability for the entire installation of SQL Server.How do you monitor always on availability groups? ›
The most basic way to get started monitoring AGs is by using the built-in dashboard in SQL Server Management Studio (SSMS). Once an AG has been created using either T-SQL or SSMS, the Always On Availability Group Dashboard can be opened in SMSS by right-clicking the Availability Databases node.Can you restore a database in an availability group? ›
Because availability database restores are not allowed on any replica of availability groups, before running the restore, you must remove the database from the availability group. After running the restore operation, you can manually add the database back to the availability group.What is the benefit of a failover cluster? ›
Failover clusters also provide Cluster Shared Volume (CSV) functionality that provides a consistent, distributed namespace that clustered roles can use to access shared storage from all nodes. With the Failover Clustering feature, users experience a minimum of disruptions in service.
How do you ensure high availability on a server? ›
- Implement multiple application servers. ...
- Scaling and slaves matters. ...
- Spread out physically. ...
- Maintain a recurring online backup system along with hardware. ...
- Use of a virtualized server for zero-downtime recovery.
The failover operation is the process of switching production to a backup facility (normally your recovery site). A failback operation is the process of returning production to its original location after a disaster or a scheduled maintenance period.What are the top reasons that cause an unsuccessful failover? ›
- Symptoms if an automatic failover is triggered successfully.
- Symptoms if an automatic failover is unsuccessful.
- Case 1: "Maximum Failures in the Specified Period" value is exhausted.
- Case 2: Insufficient NT Authority\SYSTEM account permissions.
- Case 3: The availability databases aren't in a SYNCHRONIZED state.
In SQL Server Configuration Manager, click SQL Server Services, right-click SQL Server (<instance name>), where <instance name> is the name of a local server instance for which you want to enable Always On Availability Groups, and click Properties. Select the Always On High Availability tab.How to check availability group in SQL Server? ›
Right-click the availability group whose properties you want to view, and select the Properties command. In the Availability Group Properties dialog box, use the General and Backup Preferences pages to view and, in some cases, change properties of the selected availability group.What is difference between replication and always on SQL Server? ›
AlwaysOn/Mirroring reads the log on the master server and transfers all the commands to the DR servers where it essentially restores the t-log from a backup. Replication reads the log and translates the transactions and commands into individual commands to insert/updated/delete one row at a time on the subscribers.Does SQL AlwaysOn require clustering? ›
Deploying Always On availability groups requires a Windows Server Failover Cluster (WSFC). To be enabled for Always On availability groups, an instance of SQL Server must reside on a WSFC node, and the WSFC and node must be online.How do I know if SQL Server is always on status? ›
Use ISHADRENABLED property to check the status of "Always On" availability of groups. You can use Windows PowerShell to invoke SQL command on a reachable server within the network using Invoke-Sqlcmd cmdlet as the following, Open Windows PowerShell as Administrator.How do you manually failover Alwayson availability groups? ›
In Object Explorer, connect to a server instance that hosts a secondary replica of the availability group that needs to be failed over. Expand the server tree. Expand the Always On High Availability node and the Availability Groups node. Right-click the availability group to be failed over, and select Failover.How do I change SQL Server failover mode? ›
Using SQL Server Management Studio
Right-click the replica, and click Properties. In the Availability Replica Properties dialog box, use the Failover mode drop list to change the failover mode of this replica.
What are the different types of server failover? ›
Three forms of failover exist: automatic failover (without data loss), planned manual failover (without data loss), and forced manual failover (with possible data loss), typically called forced failover.How to configure failover cluster step by step? ›
- Verify the prerequisites.
- Install the Failover Clustering feature.
- Validate the configuration.
- Create the failover cluster.
- Create clustered roles.
- Create a failover cluster by using Windows PowerShell.
- More information.
Failover servers for high availability – Allows customers to install and run passive SQL Server instances in a separate operating system environment (OSE) or server for high availability on-premises in anticipation of a failover event.What's the difference between a planned failover and the failover option when right clicking on the virtual machine and replica? ›
In the case of a “Planned Failover”, the Hyper-V Primary Server is notified of the operation/action so it takes necessary actions for the primary Virtual Machine. On the other hand, “Unplanned Failover”, which is performed at the Replica Server, does not provide any notification to the Replica Server.How do you failover a physical standby database? ›
- Step:2 Cancel the MRP process. alter database recover managed standby database cancel;
- Step:3 The below commands will help to bring up standby as primary.
- Step:5 Bounce your database and verify database name its open mode and its role.
- Right click the service and hover your cursor in move this service or application to another node, It give you an option Move to Node 2 click on the options as shown in the image.
- You will be prompted to confirm. Select to Move. ...
- And your Node2 will take ownership.
- Configure the Database Publications and Subscriptions.
- Configure the Always On Availability Group.
- Ensure that all of the Secondary Replica Hosts are Configured for Replication.
- Configure the Secondary Replica Hosts as Replication Publishers.
- Redirect the Original Publisher to the AG Listener Name.
When should I use Planned Failover? I want to perform host maintenance on my primary and would like to run from the replica site. My primary site is expecting some power outage – I want to move over to the replica site. There's an impending typhoon – I want to proactively take action to ensure business continuity.What is failover and why is it useful? ›
Failover is the ability to switch automatically and seamlessly to a reliable backup system. When a component or primary system fails, either a standby operational mode or redundancy should achieve failover and lessen or eliminate negative impact on users.What triggers an unscheduled failover? ›
An unplanned failover is a failover performed when an unexpected failure occurs resulting in a critical VM or the entire primary site going offline. The failure can be caused by any of a number of natural disasters, accidents (a power outage), a malware attack, or any other incident.
What is the difference between switchover and failover? ›
Answer: In general, a failover is a production emergency, where the primary database has failed and you need to failover to the standby database. Conversely, a switchover is a planned switch from a standby back to the primary database, a non-emergency operation.What is the difference between Dataguard switchover and failover? ›
The main difference between switchover and failover Oracle Data Guard is that Switchover requires human intervention, while failover occurs automatically without warning. In brief, switchover converts to the standby database manually while failover converts to the standby database automatically during a failure.How do you failover a cluster in SQL Server? ›
To do so, launch Add Roles and Feature Wizard from the server manager. Enable the Failover Clustering feature in both the SQL nodes. Confirm the failover cluster installation for SQL Server Always On Availability Groups.How do you simulate a failover? ›
- Open the Failover Cluster Manager on the Primary Cluster Node. For steps to open the Failover Cluster Manager, see Open and View the Failover Cluster Manager. ...
- Right-click a Resource and select More Actions, Simulate failure of this resource.
In the event of a failover, the WSFC service transfers ownership of instance's resources to a designated failover node. The SQL Server instance is then re-started on the failover node, and databases are recovered as usual. At any given moment, only a single node in the cluster can host the FCI and underlying resources.What is the difference between replication and always on? ›
AlwaysOn/Mirroring reads the log on the master server and transfers all the commands to the DR servers where it essentially restores the t-log from a backup. Replication reads the log and translates the transactions and commands into individual commands to insert/updated/delete one row at a time on the subscribers.What are the disadvantages of always on availability groups SQL Server? ›
Disadvantages. You cannot safeguard system databases (Master, Model, and MSDB) from instance or database level failure. Always On does not support adding them to the availability groups. Always On does not synchronize SQL Server logins, linked servers, and Agent jobs to the secondary databases.