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Exchange 2016 - DAG Activation Preference Change

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Microsoft released this new "Feature" called "PreferenceMoveFrequency" in Exchange 2016 CU2 - What does this mean for you as an Admin?

Previously once you did maintenance on your Mailbox Server you would need to run "RedistributeActiveDatabases.ps1" script to balance the databases again. In CU2 the above option is set by default to run every 1 hour.

What does this mean for you? The Primary Active Manager in the DAG now performs periodic discretionary moves to activate the copy that the administrator has setup/defined.

To view this you run the following command:

  • Get-databaseavailabilityGroup | fl Preference*

https://collaborationpro.com/wp-content/uploads/2017/06/preference.png

If you want to disable this option on your DAG then you can run the following command:

  • Set-DatabaseAvailabilityGroup -Identity <DAGName> -PreferenceMoveFrequency ([System.Threading.Timeout]::InfiniteTimeSpan)

To be able to take advantage of this new feature, you need to be on CU2 on Exchange 2016. Once your primary active manager is upgraded to CU2 then you can use it.

Lastly, you will need to restart the Microsoft Exchange Replication service.