Exchange 2013 DAG DB Failed

Hi all

 I have two Exchange 2013 servers in DAG, one of the DB is showing failed and suspend and its active in the second server, all other dbs are healthy and active in the first server, I tried below and got the error.

Update-MailboxDatabaseCopy -identity "DB1\MAIL1" -DeleteExistingFiles -SourceServer as mail2

The seeding operation failed. Error: An error occurred while performing the seed operation. Error: The process cannot
access the file 'e:\Program Files\Microsoft\Exchange Server\V15\Mailbox\DB1\DB1.edb' because it is being
used by another process. [Database: DB1, Server: mail1.domain.com]
    + CategoryInfo          : InvalidOperation: (:) [Update-MailboxDatabaseCopy], SeedInProgressException
    + FullyQualifiedErrorId : [Server=mail1,RequestId=5e159664-0df2-422b-85c7-89a69bb382ec,TimeStamp=8/18/2016 3:21:
   51 PM] [FailureCategory=Cmdlet-SeedInProgressException] 8D710ACC,Microsoft.Exchange.Management.SystemConfiguration
  Tasks.UpdateDatabaseCopy
    + PSComputerName        : mail1.domain.com


Please advise