• Estimated time to complete: 30 minutes
  
  
• You need to be assigned permissions before you can perform this procedure or procedures. To see what permissions you need, see the "Mailbox database copies" entry in the High Availability and Site Resilience Permissions topic.
  
  
• If Exchange is installed in a location other than the default location, you must use the /TargetDir Setup switch to specify the location of the Exchange program files. If you don't use the /TargetDir switch, the Exchange program files will be installed in the default location (%programfiles%\Microsoft\Exchange Server\V15).
  
  To determine the install location, follow these steps:
  
  
  1. Open ADSIEDIT.MSC or LDP.EXE.
     
     
  2. Navigate to the following location: CN=ExServerName,CN=Servers,CN=First Administrative Group,CN=Administrative Groups,CN=ExOrg Name,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=DomainName,CN=Com
     
     
  3. Right-click the Exchange server object, and then click Properties.
     
     
  4. Locate the msExchInstallPath attribute. This attribute stores the current installation path.
     
     
• For information about keyboard shortcuts that may apply to the procedures in this topic, see Keyboard Shortcuts in the Exchange Admin Center.
  
  

Tip:
Having problems? Ask for help in the Exchange forums. Visit the forums at: Exchange Server, Exchange Online, or Exchange Online Protection.

1. Retrieve any replay lag or truncation lag settings for any mailbox database copies that exist on the server being recovered by using the Get-MailboxDatabase cmdlet.
   
   

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   Get-MailboxDatabase DB1 | Format-List *lag*

2. Remove any mailbox database copies that exist on the server being recovered by using the Remove-MailboxDatabaseCopy cmdlet.
   
   

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   Remove-MailboxDatabaseCopy DB1\MBX1

3. Remove the failed server's configuration from the DAG by using the Remove-DatabaseAvailabilityGroupServer cmdlet.
   
   

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   Remove-DatabaseAvailabilityGroupServer -Identity DAG1 -MailboxServer MBX1

   Note:
   If the DAG member being removed is offline and can't be brought online, you must add the ConfigurationOnly parameter to the preceding command.

4. Reset the server's computer account in Active Directory. For detailed steps, see Reset a Computer Account.
   
   
5. Open a Command Prompt window. Using the original Setup media, run the following command.
   
   

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   Setup /m:RecoverServer

6. When the Setup recovery process is complete, add the recovered server to the DAG by using the Add-DatabaseAvailabilityGroupServer cmdlet.
   
   

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   Add-DatabaseAvailabilityGroupServer -Identity DAG1 -MailboxServer MBX1

7. After the server has been added back to the DAG, you can reconfigure mailbox database copies by using the Add-MailboxDatabaseCopy cmdlet. If any of the database copies being added previously had replay lag or truncation lag times greater than 0, you can use the ReplayLagTime and TruncationLagTime parameters of the Add-MailboxDatabaseCopy cmdlet to reconfigure those settings.
   
   

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   Add-MailboxDatabaseCopy -Identity DB1 -MailboxServer MBX1 Add-MailboxDatabaseCopy -Identity DB2 -MailboxServer MBX1 -ReplayLagTime 3.00:00:00 Add-MailboxDatabaseCopy -Identity DB3 -MailboxServer MBX1 -ReplayLagTime 3.00:00:00 -TruncationLagTime 3.00:00:00

To verify that you've successfully recovered the DAG member, do the following:

• In the Shell, run the following command to verify the health and status of the recovered DAG member.
  
  

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  Test-ReplicationHealth <ServerName>

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  Get-MailboxDatabaseCopyStatus -Server <ServerName>

  All of the replication health tests should pass successfully, and the status of databases and their content indexes should be healthy.