When a mailbox database copy has failed in an Exchange Server 2010 Database Availability Group (DAG) it may be necessary to reseed the mailbox server with the failed database copy.
To Reseed the database we need to suspend the replication first using command:
[PS] C:>Suspend-MailboxDatabaseCopy -Identity "Mailbox Database 01EX2"
The mailbox database copy status will now change from “Failed” to “Failed and Suspended”.
Now, we can use the command to reseed the database:
[PS] C:>Update-MailboxDatabaseCopy -Identity "Mailbox Database 01EX2" -DeleteExistingFiles
When the update has completed it will automatically resume replication for the database copy