To back up SQL, use a Backup Exec logon account that stores the credentials of a Windows user account. The Windows user account must have been granted the System Administrator role on the SQL instance.
In the backup selections list or in the resource credentials list, apply that logon account to the Windows server that SQL is installed on, not to the actual SQL instance.
If you are using SQL Server Authentication, then add a Backup Exec logon account that stores the credentials of the SQL user account.
In the backup selections list, apply the Backup Exec logon account for the Windows user account to the Windows server that SQL is installed on, and then apply the logon account for the SQL user account to the SQL instance.
If you use a Backup Exec logon account that does not have the proper rights, you will receive an error message stating that the username and password are invalid.