SQL 2016 HA Group stuck in Synchronizing

Question

SQL 2016 HA Group stuck in Synchronizing

Joseph Vetro 0

We have 2 SQL Servers in a SQL HA group for the past 7 years with no issues. We had a crash on the primary SQL Server and was able to get everything working again on primary. Now the secondary replica is in a "Synchronizing" state and has been for over almost 2 months.

Erland Sommarskog 134.1K Reputation points MVP Volunteer Moderator

2025-10-07T21:16:29.6533333+00:00

I may be missing something, but isn't SYNCHRONIZING the expected state for a healthy secondary?
Joseph Vetro 0 Reputation points

2025-10-08T12:17:07.7+00:00

No, the state needs to be "Synchronized" and "No Data Loss".
Joseph Vetro 0 Reputation points

2025-10-09T19:12:45.13+00:00

Thank you so much Erland. After investigating further, my HA Group previously was set to Synchronous, where now it is Asynchronous, hence the Synchronizing state. I now need to investigate further on how and why this was changed!
Erland Sommarskog 134.1K Reputation points MVP Volunteer Moderator

2025-10-09T20:48:07.1133333+00:00

Thanks for the update! I've converted my later comment to an Answer, in case you would like to accept it. And most likely, you want the AG to be synchronous, since this option protects you against data loss in case of a failover. (Then again, it will have an impact on performance.)

Answer recommended by moderator

0 additional answers

Your answer

Erland Sommarskog 134.1K Reputation points MVP Volunteer Moderator

2025-10-07T21:16:29.6533333+00:00

I may be missing something, but isn't SYNCHRONIZING the expected state for a healthy secondary?
Joseph Vetro 0 Reputation points

2025-10-08T12:17:07.7+00:00

No, the state needs to be "Synchronized" and "No Data Loss".
Joseph Vetro 0 Reputation points

2025-10-09T19:12:45.13+00:00

Thank you so much Erland. After investigating further, my HA Group previously was set to Synchronous, where now it is Asynchronous, hence the Synchronizing state. I now need to investigate further on how and why this was changed!
Erland Sommarskog 134.1K Reputation points MVP Volunteer Moderator

2025-10-09T20:48:07.1133333+00:00

Thanks for the update! I've converted my later comment to an Answer, in case you would like to accept it. And most likely, you want the AG to be synchronous, since this option protects you against data loss in case of a failover. (Then again, it will have an impact on performance.)

Answer 1

Erland Sommarskog 134.1K MVP Volunteer Moderator

I'm looking at the topic for sys.dm_hadr_database_replica_states and I see this: User's image

So you would only see SYNCHRONIZED if the secondary has caught up with the primary. Which can be difficult if there is constant activity.

I look at my own AGs that I have here at home, and all my secondaries are SYNCHRONIZING, despite the primary databases all being idle. To note is that these are clusterless AGs and all replicas are asynchronous, so they can never be SYNCHRONIZED.

And maybe that is your issues: Your replicas are set up to be asynchronous?

Shruti Dhruv 875 Reputation points Microsoft External Staff Moderator

2025-10-17T11:49:02.6766667+00:00

Hi @Joseph Vetro ,

I hope the information provided above assists you in resolving the issue. If you have any additional questions, please feel free to reach out.

Thank You
Shruti Dhruv 875 Reputation points Microsoft External Staff Moderator

2025-10-21T12:37:38.92+00:00

Hi @Joseph Vetro ,

I hope the information provided above assists you in resolving the issue. If you have any additional questions, please feel free to reach out.

Thank You

Share via

SQL 2016 HA Group stuck in Synchronizing

0 additional answers

Your answer