“Unlock Instant Performance Gains with Lesson Learned #337: Troubleshooting HADR_SYNC_COMMIT Wait Type Delays in Azure SQL Database”

Lesson Learned #337: HADR_SYNC_COMMIT wait type delay in Azure SQL Database
Overview
The Azure Database Support team has identified an issue related to the HADR_SYNC_COMMIT wait type in Azure SQL Database. This wait type shows up when replicating databases in a high availability group and can cause replication delays. In this post, we’ll discuss how to identify the issue, how to troubleshoot it, and how to prevent it from happening in the future.

Identifying the Issue
The HADR_SYNC_COMMIT wait type occurs when replicating databases in a high availability group in Azure SQL Database. It can cause replication delays and can be difficult to identify. To spot the issue, you should monitor the wait stats of your secondary databases. If you find that the wait time for HADR_SYNC_COMMIT is high, then you may have identified the issue.

Troubleshooting the Issue
Once you’ve identified the issue, the next step is to troubleshoot it. The first thing you should do is verify that the Azure SQL Database secondary is online and that the replication is working correctly. You can do this by checking the status of the secondary in the Azure portal. If the secondary is online and the replication is working properly, then you can move on to the next step.

The next step is to check the replication latency of your secondary databases. If the latency is high, then it’s likely that the HADR_SYNC_COMMIT wait type is causing the delay. To further diagnose the issue, you should look at the wait stats of your secondary databases to identify any other wait types that may be contributing to the delay.

Preventing the Issue in the Future
The best way to prevent the HADR_SYNC_COMMIT wait type from occurring in the future is to ensure that your replication latency is as low as possible. You can do this by optimizing the queries on your primary databases, scaling up your hardware resources, or using read-only routing to offload read-only workloads from your primary databases.

You should also monitor the wait stats of your secondary databases on a regular basis to ensure that the HADR_SYNC_COMMIT wait type is not occurring. If it is, then you should take steps to address the issue right away.

Conclusion
The HADR_SYNC_COMMIT wait type can be difficult to identify and can cause replication delays in Azure SQL Database. To prevent the issue from occurring in the future, you should ensure that your replication latency is as low as possible and monitor the wait stats of your secondary databases on a regular basis.
References:
Lesson Learned #337: HADR_SYNC_COMMIT wait type delay in Azure SQL Database
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1. Azure SQL Database HADR_SYNC_COMMIT
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