Managing DAG: Adding nodes and DAC mode

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In this Tutorial of our Managing DAG in Exchange Server 2013 series we will be adding additional nodes to our newly created DAG and also configuring it to use DAC mode.

In the first article of this series we shown the big picture with two datacenters and a DAG witness server located in a third datacenter.

At this point in the series we are finishing up one of the sides (Toronto Datacenter) where we configured the first member and built the DAG and in this post we will be adding the second node and configuring the DAC mode.


Adding additional members to the DAG…

The process is straight forward and you have done that before adding your first node, the only requirements is to make sure that you have consistency of the configurations (mainly network and disk) with the existent nodes.

In order to add one or several DAG members, just open EAC, servers, click on database availability groups and click on manage database availability group membership and on the new page, click on add (+ icon) and then click on save.


The process like we saw in the previous article may take some minutes, just hang in there and the process will finish successfully as displayed in image below.


Configuring the DAG to Datacenter Activation Coordination (DAC) mode..


The DAC mode should be enable on any DAG to avoid split brain syndrome where we have in any given time two sides of a cluster active which is a nightmare to any messaging administrator. By default DAC is disabled when creating a new DAG.

Note: If you use a third-party replication mode in your DAG, then you should leave the default settings which is DAC mode disabled.

In order to retrieve the information of your existent DAG, just run Get-DatabaseAvailabilityGroup | ft Name,MemberServers,Datacenter* cmdlet from your Exchange Management Shell and a list of all DAG objects, members and current configuration of your DAC mode will be listed.

In order to change any given DAG, just run the following syntax: Set-DatabaseAvailabilityGroup –Identity <DAGName> –DatacenterActivationMode DAGOnly

All cmdlets can be seen in action in the image below.


More information:

  • DAC in Exchange Server 2013

Written by Anderson Patricio

Anderson Patricio

Anderson Patricio is a Canadian MVP in Cloud and Datacenter Management, and Office Server and Services, besides the Microsoft Award he also holds a Solutions Master (MCSM) in Exchange and several other certifications. Anderson has been contributing to the Microsoft Community with articles, tutorials, blog posts, twitter, forums and book reviews. He is a regular contributor here at,, and Anderson (Portuguese).

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