You're unable to activate database copy on Exchange 2010 mailbox server

If you receive the following error message when you try to activate mailbox copy one some of your DAG member servers :

An Active Manager operation failed. Error: An error occurred while trying to validate the specified database copy for possible activation. Error: Database copy 'Mailbox Database 01' on server 'Server3.domain.name' has content index catalog files in the following state: 'Failed'..

You can check the status of the mailbox database content index with :

Get-MailboxDatabaseCopyStatus | fl name, contentindexstate

Name              : Mailbox Database 01\Server3
ContentIndexState : Failed

Name              : Mailbox Database 02\Server3
ContentIndexState : Healthy

Also on the mailbox server where the content index is corrupted you can see the following event:

Event ID: 123
Level: Error
Source: ExchangeStoreDB

At <timestamp> the Microsoft Exchange Information Store Database <identity> copy on this server experienced a corrupted search catalog. Consult the event log on the server for other "ExchangeStoreDb" and "MSExchange Search Indexer" events for more specific information about the failure. Reseeding the catalog is recommended via the 'Update-MailboxDatabaseCopy' task.

To resolve this problem you can update content index on failed server with Update-MailboxDatabaseCopy  http://technet.microsoft.com/en-us/library/ee633475.aspx :

Update-MailboxDatabaseCopy "Mailbox Database 01\Server3" -CatalogOnly

After reseeding, the content index should be in healthy state:

Get-MailboxDatabaseCopyStatus | fl name, contentindexstate

Name : Mailbox Database 01\Server3
ContentIndexState : Healthy

Name : Mailbox Database 02\Server3
ContentIndexState : Healthy

Now, you can succesfully activate Mailbox Database 01 on Server 3.