How to Block Automatic Database Activation on an Exchange DAG Member

Applies to: Exchange Server SE / 2019 / 2016 / 2013 / 2010

In an Exchange Database Availability Group (DAG), you can prevent a Mailbox server from being selected for automatic database activation. This is useful when a DAG member should keep passive database copies but should not automatically host an active copy after a failure.

The original version of this article described this as “manual failover.” A more accurate description is blocking automatic database activation on a DAG member.

In This Article

• 1. Block Automatic Database Activation
• 2. What Blocked Does and Does Not Do
• 3. Allow Automatic Activation Again
• 4. Maintenance Mode Is Different
• 5. Key Takeaways

1. Block Automatic Database Activation

To prevent database copies on a specific DAG member from being automatically activated, set the server-level database copy activation policy to Blocked:

Set-MailboxServer -Identity EX01 -DatabaseCopyAutoActivationPolicy Blocked

Replace EX01 with the Exchange server name.

Microsoft also provides IntrasiteOnly, which allows automatic activation only when the active and passive copies are in the same Active Directory site.

2. What Blocked Does and Does Not Do

• Blocked prevents automatic activation of database copies on the selected server.
• Replication to passive database copies continues. Log shipping and replay are not disabled by this setting.
• Databases that are already active on the server are not automatically moved elsewhere just because the policy is changed to Blocked.
• An administrator can still manually activate a database copy on a server whose automatic activation policy is Blocked.

3. Allow Automatic Activation Again

To return the server to the default activation behavior, set the policy back to Unrestricted:

Set-MailboxServer -Identity EX01 -DatabaseCopyAutoActivationPolicy Unrestricted

You can verify the current setting with Get-MailboxServer and review the DatabaseCopyAutoActivationPolicy property.

4. Maintenance Mode Is Different

Do not use DatabaseCopyAutoActivationPolicy Blocked by itself as a complete server maintenance procedure. It does not drain transport, move all active databases, pause the cluster node, or place Exchange server components into maintenance state.

For patching or planned server maintenance, use the normal DAG maintenance process. Exchange includes StartDagServerMaintenance.ps1 and StopDagServerMaintenance.ps1, which handle the additional DAG actions required for maintenance.

5. Key Takeaways

• Use Blocked when a DAG member should not automatically activate mailbox database copies.
• The setting does not stop database replication.
• The setting does not move databases that are already active on the server.
• Use Unrestricted to restore normal automatic activation behavior.
• Use the full DAG maintenance procedure for patching or planned server maintenance.

References

• Microsoft Learn – Manage database availability groups
• Microsoft Learn – Manage mailbox database copies
• Microsoft Learn – Set-MailboxServer