| title | Enable the availability group feature for a SQL Server instance | ||
|---|---|---|---|
| description | Describes how to enable the Always On availability group feature for an instance of SQL Server. | ||
| author | MashaMSFT | ||
| ms.author | mathoma | ||
| ms.reviewer | maghan | ||
| ms.date | 02/01/2024 | ||
| ms.service | sql | ||
| ms.subservice | availability-groups | ||
| ms.topic | how-to | ||
| helpviewer_keywords |
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[!INCLUDE SQL Server]
This article contains information about the requirements for configuring an instance of [!INCLUDE ssNoVersion] to support [!INCLUDE ssHADR] in [!INCLUDE ssnoversion].
Important
For essential information about [!INCLUDE ssHADR] prerequisites and restrictions for Windows Server Failover Clustering (WSFC) nodes and instances of [!INCLUDE ssNoVersion], see Prerequisites, Restrictions, and Recommendations for Always On Availability Groups (SQL Server).
Always On Availability Groups
A high-availability and disaster-recovery solution that provides an enterprise-level replacement for database mirroring. An availability group supports a failover environment for a discrete set of user databases, known as availability databases, that fail over together.
Availability replica An instantiation of an availability group hosted by a specific instance of [!INCLUDE ssNoVersion] and that maintains a local copy of each availability database that belongs to the availability group. Two availability replicas exist: a single primary replica and one to four secondary replicas. The server instances that host the availability replicas for a given availability group must reside on different nodes of a single Windows Server Failover Clustering (WSFC) cluster.
database mirroring endpoint
An endpoint is an SQL Server object that enables SQL Server to communicate over the network. To participate in database mirroring and/or [!INCLUDE ssHADR] a server instance requires a unique, dedicated endpoint. All mirroring and availability group connections on a server instance use the same database mirroring endpoint. This special-purpose endpoint is used exclusively to receive these connections from other server instances.
To support [!INCLUDE ssHADR], a server instance must reside on a node in the WSFC failover cluster that hosts the availability group, be [!INCLUDE ssHADR] enabled and possessed a database mirroring endpoint.
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Enable the Always On Availability Groups feature on every server instance to participate in one or more availability groups. A given server instance can host only a single availability replica for a given availability group.
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Ensure that the server instance possesses a database mirroring endpoint.
To enable Always On Availability Groups
To determine whether a database mirroring endpoint exists
To create a database mirroring endpoint
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Create a Database Mirroring Endpoint for Always On Availability Groups (SQL Server PowerShell)
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Create a Database Mirroring Endpoint for Windows Authentication (Transact-SQL)
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Allow a Database Mirroring Endpoint to Use Certificates for Outbound Connections (Transact-SQL)
- Always On - HADRON Learning Series: Worker Pool Usage for HADRON Enabled Databases
- SQL Server Always On Team Blogs: The official SQL Server Always On Team Blog
- CSS SQL Server Engineers Blogs
- Microsoft SQL Server Always On Solutions Guide for High Availability and Disaster Recovery
- SQL Server Customer Advisory Team Whitepapers
- Overview of Always On Availability Groups (SQL Server)
- Prerequisites, Restrictions, and Recommendations for Always On Availability Groups (SQL Server)
- The Database Mirroring Endpoint (SQL Server)
- Always On Availability Groups: Interoperability (SQL Server)
- Failover Clustering and Always On Availability Groups (SQL Server)
- Windows Server Failover Clustering (WSFC) with SQL Server
- Always On Failover Cluster Instances (SQL Server)