Although it’s documented on our TechNet however I always receive a question for how to install a RU on DAG members, so to make it easier here is the simple steps to do so:

  1. Use the StartDagServerMaintenance.ps1 script to put the DAG member in maintenance mode
  2. Install the update rollup
  3. Use the StopDagServerMaintenance.ps1 script to take the DAG member out of maintenance mode and put it back into production
  4. Use the RedistributeActiveDatabases.ps1 script to re-balance the active database copies across the DAG

The StartDagServerMaintenance.ps1 performs the following tasks:

  1. It runs Suspend-MailboxDatabaseCopy for each database copy hosted on the DAG member.
  2. It pauses the node in the cluster, which prevents it from being and becoming the PAM.
  3. It sets the value of the DatabaseCopyAutoActivationPolicy parameter on the DAG member to Blocked.
  4. It moves all active databases currently hosted on the DAG member to other DAG members.
  5. If the DAG member currently owns the default cluster group, it moves the default cluster group (and therefore the PAM role) to another DAG member

The StopDagServerMaintenance.ps1 performs the following tasks:

  1. It run Resume-MailboxDatabaseCopy for each database copy hosted on the DAG member.
  2. It resumes the node in the cluster, which it enables full cluster functionality for the DAG member.
  3. It sets the value of the DatabaseCopyAutoActivationPolicy parameter on the DAG member to Unrestricted.

Hope that this helpsSmile