Wait Type HADR_DBR_SUBSCRIBER_FILTER_LIST

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 provide robust high availability and disaster recovery options, but they also come with unique wait types that can indicate how the system is performing. One such wait type is HADR_DBR_SUBSCRIBER_FILTER_LIST. Understanding this wait type is key to maintaining a healthy Always On environment.

What is HADR_DBR_SUBSCRIBER_FILTER_LIST?

The HADR_DBR_SUBSCRIBER_FILTER_LIST wait type occurs when SQL Server is managing or accessing the filter list for database replication subscribers in an Always On Availability Group. This wait type typically appears during synchronization or when filtering the list of eligible replicas for receiving updates from the primary replica.

In simpler terms, this wait reflects the time spent ensuring the right replicas are synchronized as part of the Always On setup. While some waits are expected, prolonged or frequent occurrences can indicate inefficiencies or bottlenecks in your configuration or workload.

Why Does HADR_DBR_SUBSCRIBER_FILTER_LIST Happen?

Several factors can lead to HADR_DBR_SUBSCRIBER_FILTER_LIST waits, including:

• High transaction volume, leading to increased workload for replica synchronization.
• Slow or unreliable network connections between the primary and secondary replicas.
• Resource contention, such as insufficient CPU, memory, or disk I/O capacity on either the primary or secondary replicas.
• Complex Always On Availability Group configurations involving multiple replicas.
• Heavy workloads causing delays in managing and applying subscriber filters.

These factors can contribute to delays in replica synchronization, impacting performance and availability.

How to Monitor HADR_DBR_SUBSCRIBER_FILTER_LIST Waits

To understand and manage HADR_DBR_SUBSCRIBER_FILTER_LIST waits, monitoring is essential. The Database Health Monitor is a powerful tool that helps you track wait types, including this one, over time. Its Historic Waits Monitoring feature provides insights into when these waits occur and their frequency.

With Database Health Monitor, you can identify patterns and correlate them with system activity, helping you pinpoint root causes and take the necessary corrective actions.

What Can You Do About HADR_DBR_SUBSCRIBER_FILTER_LIST Waits?

If you encounter frequent or prolonged HADR_DBR_SUBSCRIBER_FILTER_LIST waits, consider the following actions:

• Optimize your Always On Availability Group configuration to reduce complexity and improve synchronization efficiency.
• Ensure adequate CPU, memory, and disk I/O resources are available on both primary and secondary replicas.
• Upgrade network bandwidth and reliability to minimize latency between replicas.
• Analyze transaction volume and optimize queries or indexes to reduce workload on the primary replica.
• Monitor and address contention on heavily used replicas by distributing workloads more effectively.

These steps can help reduce synchronization delays and improve the performance of your Always On environment.

How Stedman Solutions Can Help

At Stedman Solutions, we specialize in SQL Server performance optimization and troubleshooting, including resolving wait types like HADR_DBR_SUBSCRIBER_FILTER_LIST. Our managed services provide proactive support and expert guidance to keep your Always On Availability Groups running efficiently. Additionally, our Database Health Monitor offers comprehensive tools for tracking and analyzing SQL Server waits, helping you maintain a reliable and high-performing database environment.

If you’re facing challenges with your Always On setup or need assistance optimizing your SQL Server environment, contact us today. Let us help you achieve a robust and efficient SQL Server environment!

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Applies to

Related Waits

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• More About HADR_DBR_SUBSCRIBER_FILTER_LIST