Hello
On Windows Server 2003 system, if you plan to use Integrated authentication to connect to
an SQL Server instance, you need to restart the Data Protector Inet service under a
Windows domain user account that has the appropriate SQL Server permissions for running
backups and restores.
From Microsoft documentation we can see the following:
http://technet.microsoft.com/en-us/library/cc966495.aspx#E0DB0AA
Virtual Device Interface
Virtual Device Interface (VDI) is the programming interface for the Backup Restore API. It provides function calls to manipulate the backup and restore functionality in SQL Server.
VDI is used by several third-party tools that provide capabilities to back up SQL Server databases. For more information on this topic, see “Virtual Backup Device Samples” in SQL Server Books Online.
Permissions Required for Backup and Restore
Any logon that requires permissions to perform backup or restore operations should be provided membership in the following SQL Server roles:
Server Role : sysadmin
DB role : db_backupoperator, dbo_owner
Permissions required for performing restore -
Server role : sysadmin, dbcreator
DB role : db_owner
And From DP integration guide:
Using the SQL Server Management Studio, add the user account which you will use for backing
up and restoring SQL Server data to the fixed server role sysadmin. For instructions, see the
SQL Server documentation
The user must be member of sysadmin group for to be able take backup. Please let me know if you need something else.