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Policy based management for operational issues with Always On availability groups

  • Artikkeli

Applies to: SQL Server

The Always On availability groups health model evaluates a set of predefined policy based management (PBM) policies. You can use these for viewing the health of an availability group and its availability replicas and databases in SQL Server.

Terms and Definitions

Always On predefined policies
A set of built-in policies that allow a database administrator to check an availability group and its availability replicas and databases for compliance with the states that are defined by the Always On policies.

Always On availability groups
A high-availability and disaster-recovery solution that provides an enterprise-level alternative to database mirroring.

availability group
A container for a discrete set of user databases, known as availability databases, that fail over together.

availability replica
An instantiation of an availability group that is hosted by a specific instance of SQL Server and that maintains a local copy of each availability database that belongs to the availability group. Two types of 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.

availability database
A database that belongs to an availability group. For each availability database, the availability group maintains a single read-write copy (the primary database) and one to four read-only copies (secondary databases).

Always On Dashboard
A SQL Server Management Studio dashboard that provides an at-a-glance view of the health of an availability group. For more information, see Always On Dashboard, later in this article.

Predefined Policies and Issues

The following table summarizes the predefined policies.

Policy name Issue Category***** Facet
WSFC Cluster State WSFC cluster service is offline. Critical Instance of SQL Server
availability group Online State Availability group is offline. Critical Availability group
availability group Automatic Failover Readiness Availability group isn't ready for automatic failover. Critical Availability group
Availability Replicas Data Synchronization State Some availability replicas aren't synchronizing data. Warning Availability group
Synchronous Replicas Data Synchronization State Some synchronous replicas aren't synchronized. Warning Availability group
Availability Replicas Role State Some availability replicas don't have a healthy role. Warning Availability group
Availability Replicas Connection State Some availability replicas are disconnected. Warning Availability group
Availability Replica Role State Availability replica doesn't have a healthy role. Critical Availability replica
Availability Replica Connection State Availability replica is disconnected. Critical Availability replica
Availability Replica Join State Availability replica isn't joined. Warning Availability replica
Availability Replica Data Synchronization State Data synchronization state of some availability database isn't healthy. Warning Availability replica
Availability Database Suspension State Availability database is suspended. Warning Availability database
Availability Database Join State Secondary database isn't joined. Warning Availability database
Availability Database Data Synchronization State Data synchronization state of availability database isn't healthy. Warning Availability database

Important

* For Always On policies, the category names are used as IDs. Changing the name of an Always On category would break its health-evaluation functionality. Therefore, do not modify the names of Always On categories.

Always On Dashboard

The Always On Dashboard gives you an at-a-glance view of the health of an availability group. The Always On Dashboard includes the following features:

  • Enables you to easily display details about a given availability group, its availability replicas, and its databases.

  • Displays visual indications of key states to help database administrators make quick operational decisions.

  • Provides launch points for troubleshooting scenarios.

  • For a given operational issue, populates the Policy Evaluation Result dialog box with information about specific Always On health policy violations and with links to remediation help.

  • Provides a health extended event viewer to show previous events for Always On-specific issues.

  • If failing over the availability group is a possible remediation for an issue, provides a launch point for the linksFail Over availability group Wizard. This wizard takes a database administrator through the manual failover process.

Extend the Always On Health Model

Extending the Always On availability groups health model is simply a matter of creating your own user-defined policies and putting them into certain categories based on the type of object that you're monitoring. After you alter a few settings, the Always On dashboard automatically evaluates your own user-defined policies, as well as the Always On predefined policies.

A user-defined policy can use any of the available PBM facets, including those used by the Always On predefined policies (see [Predefined Policies and Issues](#Always OnPBM), earlier in this article). The Server facet provides the following properties for monitoring Always On availability groups health: (IsHadrEnabled and HadrManagerStatus). The Server facet also provides properties the following policies for monitoring the WSFC cluster configuration: ClusterQuorumType, and ClusterQuorumState.

For more information, see The Always On Health Model Part 2--Extending the Health Model (a SQL Server Always On Team blog).

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