Upgrade your Exchange 2010 server roles in the following order:

1. Client Access
2. Hub Transport
3. Unified Messaging
4. Mailbox

Upgrade only passive servers: move all active mailbox database copies off the server to be upgraded and configure the server to be blocked from activation.

Prevent the DAG member from becoming a failover target by running the following command.

Set-MailboxServer –Identity mbxwithpassivdb -DatabaseCopyAutoActivationPolicy:Blocked

( Enable the upgraded DAG member to become a failover target by running the following command.

Set-MailboxServer –Identity mbxwithpassivdb -DatabaseCopyAutoActivationPolicy:Value 

The DatabaseCopyAutoActivationPolicy parameter can take 3 possible values:

Blocked
Prevent automatic database activation on selected mailbox server;

IntrasiteOnly
Only allow automatic activation within the same Active Directory site to prevent cross-site failover;

Unrestricted
No restrictions.

If the server to be upgraded currently holds the primary Active Manager role, move the role to another DAG member prior to performing the upgrade. You can determine which DAG member holds the primary Active Manager role by running

Get-DatabaseAvailabilityGroup <DAGName> -Status | Format-List PrimaryActiveManager

If necessary, move the primary Active Manager role to another DAG member by running the following command.

Cluster group "cluster group" /move

 Place Server in Maintenance mode. Before applying Updates to any DAG member, you may want to adjust monitoring applications that are in use so that the server doesn't generate alerts or alarms during the upgrade.

 Stop any processes that might interfere with the upgrade. Stop any scheduled tasks (Backup) or other processes running on the DAG member or within that DAG that could adversely affect the DAG member being upgraded or the upgrade process.

 Verify the DAG is healthy. Before applying Updates to any DAG member, we recommend that you verify the health of the DAG and its mailbox database copies. A healthy DAG will pass MAPI connectivity tests (Test-MAPIConnectivity) to all active databases in the DAG, will have mailbox database copies with a copy queue length and replay queue length that's very low, if not 0, as well as a copy status and content index state of Healthy.

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