One issue you might want to avoid if you're implementing a multi site Database Availability Group is automatic activation of copies in other sites.
For example, if you've got a Disaster Recovery site hosting copies of databases it's unlikely that during server maintenance or even just an unexpected reboot that you'll want the copies hosted in your DR site to become the Active database copies for your organization.
In this tip we'll have a look at how to prevent automatic activation on the Mailbox Servers, which in our example will be the DR site, as shown below:
As you can see above, we've got 4 Exchange Mailbox servers within a single Database Availability Group. In day-to-day use, the Head Office site will host Active mailbox database copies, and in the event of a single server failure, even without preventing database activation we'll expect the copies to activate only in the Head Office site. To account for any other issues, we can prevent Automatic Activation of Databases in the DR site by using the following Exchange Management Shell cmdlet against the Exchange Mailbox servers in the DR site:
Set-MailboxServer -Identity EXDR01 -DatabaseCopyAutoActivationPolicy IntrasiteOnly Set-MailboxServer -Identity EXDR02 -DatabaseCopyAutoActivationPolicy IntrasiteOnly
This will prevent the DR Exchange server from automatically activating database copies from the Head Office site; however if we've actively chosen to fail over to the DR site or explicitly choose to host an Active Mailbox database copy there, they will failover automatically within the DR site as expected.