You have an Exchange organization. All servers in the organization have Exchange Server 2010 SP1 installed.

The organization contains a database availability group (DAG) named DAG1. DAG1 contains two Mailbox servers named Server1 and Server2. Five databases are replicated in DAG1.

You need to install Exchange rollup updates on Server1. The solution must not prevent users from accessing their mailboxes.

What should you do first?

A.
Run the Set-DatabaseAvailabilityGroup cmdlet, and then enable Datacenter Activation co-ordination for DAG1.

B.
Run the Set-MailboxDatabase cmdlet, and then configure all mailbox database copies as lagged copies.

C.
Run the Suspend-MailboxDatabaseCopy cmdlet, and then switch over all mailbox databases to Server2.

D.
Run the UpdatemailboxDatabaseCopy cmdlet, and then modify the mailbox database Activiation preference.

Explanation:
In situations where you have a planned outage/maintenance window or if you perhaps need to seed a database, the first step is to suspend replication for the involved database(s). This can be done both via the Exchange Management Console (EMC) and the Exchange Management Shell (EMS). To do so via the EMC, you simply right-click on the respective database copy/copies and select suspend in the context menu.

To do the same via the EMS, you can use the following command:

Suspend-MailboxDatabaseCopy Identity MDB02\E14EX02

However, I don’t like this answer as in the technet article they list several powershell scripts: StartDagServerMaintenance.ps1, StopDagServerMaintenance.ps1, and RedistributeActiveDatabases.ps1. Of course, the first thing the StartDagServerMaintenance.ps1 script does is run Suspend-MailboxDatabaseCopy.

Reference:

http://technet.microsoft.com/en-us/library/dd298065.aspx
http://www.msexchange.org/articles_tutorials/exchange-server-2010/high-availability-recovery/uncovering-exchange-2010-database-availability-groups-dags-part4.html