In this Video In Hindi Jagvinder Singh Thind shows how to Configure Mailbox Database Copies in DAG (Database Availability Group) in Exchange Server 2010 in hindi. Exchange 2010 training in Hindi. A database availability group (DAG) is the base component of the high availability built into Microsoft Exchange Server 2010. A DAG is a group of up to 16 Mailbox servers that hosts a set of databases and provides automatic database-level recovery from failures that affect individual servers or databases.