Wait Type HADR_RECOVERY_WAIT_FOR_CONNECTION

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 ensure high availability and disaster recovery by maintaining synchronization between replicas. During certain operations, such as recovery or failover, you may encounter the HADR_RECOVERY_WAIT_FOR_CONNECTION wait type. Understanding this wait type can help you troubleshoot potential issues and optimize your Always On environment.

What is HADR_RECOVERY_WAIT_FOR_CONNECTION?

The HADR_RECOVERY_WAIT_FOR_CONNECTION wait type occurs when SQL Server is waiting for a connection to be established between the primary replica and a secondary replica during the recovery process. This typically happens after a failover or when a replica is being reconnected to the Always On Availability Group.

In simpler terms, this wait type means SQL Server is pausing while it tries to connect a secondary replica back into the Always On setup. While some waiting is normal during these processes, excessive waits may indicate problems with network connectivity, resource availability, or configuration settings.

Why Does HADR_RECOVERY_WAIT_FOR_CONNECTION Happen?

Several factors can lead to HADR_RECOVERY_WAIT_FOR_CONNECTION waits, including:

• Network issues between the primary and secondary replicas, such as latency or packet loss.
• Secondary replicas being offline or unavailable during the recovery process.
• Resource constraints, such as limited CPU, memory, or disk I/O on the primary or secondary replicas.
• Misconfigured Always On Availability Group settings that prevent proper communication between replicas.
• High workloads or contention on the servers hosting the replicas.

Addressing these factors can help reduce the duration of this wait type and improve overall system performance.

How to Monitor HADR_RECOVERY_WAIT_FOR_CONNECTION Waits

Monitoring HADR_RECOVERY_WAIT_FOR_CONNECTION waits is essential for identifying trends and pinpointing issues. The Database Health Monitor is an excellent tool for tracking these waits. Its Historic Waits Monitoring feature allows you to analyze when these waits occur, their frequency, and their correlation with system events.

Using Database Health Monitor, you can determine whether these waits are tied to specific replicas, network conditions, or system workloads, helping you take targeted corrective actions.

What Can You Do About HADR_RECOVERY_WAIT_FOR_CONNECTION Waits?

If you’re experiencing frequent or prolonged HADR_RECOVERY_WAIT_FOR_CONNECTION waits, consider taking the following steps:

• Check network connectivity between the primary and secondary replicas to ensure low latency and reliability.
• Verify that all secondary replicas are online and properly configured to connect to the Always On Availability Group.
• Increase system resources, such as CPU, memory, or disk I/O, on replicas that are under resource pressure.
• Optimize workloads to reduce contention and free up resources during recovery processes.
• Review and adjust Always On Availability Group settings to ensure compatibility with your workload and environment.

These measures can help you reduce recovery delays and improve the overall efficiency of your Always On Availability Group.

How Stedman Solutions Can Help

At Stedman Solutions, we specialize in SQL Server performance tuning and troubleshooting, including resolving issues with wait types like HADR_RECOVERY_WAIT_FOR_CONNECTION. Our managed services provide proactive monitoring and expert support to keep your Always On Availability Groups running smoothly. Additionally, our Database Health Monitor offers powerful tools to track and analyze SQL Server waits, ensuring your database system is reliable and efficient.

If you’re facing challenges with Always On synchronization or need help optimizing your SQL Server environment, contact us today. Let us help you achieve a high-performing and resilient database system!

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Applies to

Related Waits

See Also

• More About HADR_RECOVERY_WAIT_FOR_CONNECTION