Wait Type HADR_REPLICAINFO_SYNC

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a "wait" and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.

SQL Server Always On Availability Groups are designed to synchronize data and maintain high availability across replicas. One wait type that plays a role in this process is HADR_REPLICAINFO_SYNC. Knowing what this wait type represents can help you troubleshoot and improve the performance of your Always On environment.

What is HADR_REPLICAINFO_SYNC?

The HADR_REPLICAINFO_SYNC wait type occurs when SQL Server is synchronizing metadata and status information about replicas in an Always On Availability Group. This wait typically appears when the primary replica is sharing updates about the status, health, and configuration of replicas with other nodes in the group.

In simpler terms, this wait type indicates SQL Server is ensuring all replicas are aware of each others status and configurations to maintain proper synchronization. While some waits are expected, frequent or prolonged waits can point to issues in your Always On setup.

Why Does HADR_REPLICAINFO_SYNC Happen?

Several factors can contribute to HADR_REPLICAINFO_SYNC waits, including:

• High activity in the Availability Group, leading to frequent metadata updates.
• Network latency or bandwidth limitations between the primary and secondary replicas.
• Resource bottlenecks such as insufficient CPU or memory on the primary or secondary replicas.
• Contention caused by multiple concurrent operations in the Availability Group.
• Misconfigured Always On Availability Group settings or insufficient infrastructure for the workload.

Understanding these factors is key to identifying and addressing potential bottlenecks in synchronization.

How to Monitor HADR_REPLICAINFO_SYNC Waits

To effectively track and analyze HADR_REPLICAINFO_SYNC waits, monitoring tools are essential. The Database Health Monitor is a powerful solution for monitoring wait types, including this one. Its Historic Waits Monitoring feature allows you to observe patterns, identify when and why these waits occur, and correlate them with system activity.

By using Database Health Monitor, you can gain insights into the root causes of these waits, whether they stem from network latency, resource limitations, or high workloads, and take steps to optimize your environment.

What Can You Do About HADR_REPLICAINFO_SYNC Waits?

If you experience frequent or prolonged HADR_REPLICAINFO_SYNC waits, consider the following steps:

• Ensure that the network connections between replicas are reliable, with sufficient bandwidth and low latency.
• Allocate adequate CPU, memory, and disk I/O resources on the servers hosting the replicas.
• Optimize workloads on the primary replica to reduce metadata update frequency and contention.
• Distribute workloads across replicas to prevent overloading a single node in the Availability Group.
• Review and fine-tune Always On Availability Group configurations to align with workload demands and best practices.

These measures can help reduce synchronization delays and improve the overall performance of your Always On Availability Groups.

Why Use Database Health Monitor?

The Database Health Monitor is an invaluable tool for tracking and analyzing SQL Server waits like HADR_REPLICAINFO_SYNC. It provides detailed insights into wait types, helping you pinpoint and address performance issues effectively. With its Historic Waits Monitoring feature, you can keep your Always On environment optimized and reliable.

Start using Database Health Monitor today to maintain a high-performing SQL Server setup and ensure your Availability Groups are running smoothly!

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Applies to

Related Waits

See Also

• More About HADR_REPLICAINFO_SYNC