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DAG activation preference behavior change in Exchange 2016 CU2

Microsoft posted a blog about the new DAG activation preference behavior. It changed from Exchange 2016 CU2. For some, this will be great news. For some, it isn’t. It depends on how you are designing and deploying the Exchange DAG environment. If you want that the DAG to automatically activate databases back to the preferred one, leave it as it is.

By default, the Replication service will inspect the database copies. After that it will perform a re-balance every one hour. Microsoft recommends taking advantage of this behavior. This will ensure that the DAG remains proper balanced.

If you find a 1-hour interval too high, you can disable the new feature in Exchange 2016 CU2 and higher. Instead of automatic, you will activate the preferred database copy manual. In this article, you will learn how to disable the new feature.

DAG activation preference behavior disable

First, you need to check how the DAG preference move frequency is set. Run Exchange Management Shell as Administrator and run the following command:

The default of 1 hour is set. Let’s disable it.

You can change the interval to your preference. You don’t have to disable the new DAG activation preference behavior. If you like to have it checked every 24 hours instead, you can change the time from 00:00:00 to 24:00:00.

Run the following command to check if it’s changed to 00:00:00:

The move frequency changed to 00:00:00, which means it’s disabled. The databases will not automatically get back to their preferred database copy.


Microsoft did a good job of introducing the new DAG activation preference behavior. For the ones that do not like the change, they can change it as described in this post. If you enjoyed this article, you may also like SuspendWhenReadyToComplete Exchange. Don’t forget to follow us.



ALI TAJRAN is a passionate IT Architect and IT Consultant. His specialism is designing and building complex enterprise environments. He started Information Technology at a very young age, and his goal is to teach and inspire others. Connect with ALI TAJRAN on social media. Read more »

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