In the Symantec Backup Exec 15 Administrators Guide on page 861 you can read:
"On the Back Up Virtual Machine
dialog box, select the backup method
that you want to use for this virtual
machine, either Virtual-based backup
or Agent-based backup, and then click
everything i tried, i never get this choice :( ... what i'm doing wrong?
The selected server is correctly marked as "Windows computer (virtual machine)". In the menu "Backups", i tried to select Backup => Back Up to Disk. Now i get the "Backup Definition Properties"-Dialogue but not the expected choice... Where is the missing link to be able to make a virtual-based backup?
...you need to license the hypervisor you're trying to access, ie. Hyper-V or VMware.
Check the BE 15 licensing guide below:
Once done you can follow the Admin Guide to access the hypervisor appropriately and then backup the entire VMs.
In addition to the above, virtual-based backup options are available ONLY if you create the backup definition directly via the hypervisor (virtual host) and not via the virtual machine directly.
Create a backup job by selecting the virtual host and then select the VMs. This is a virtual-based backup. Do note, if Application GRT is enabled, the VMs will still require the remote agent installed inside them to collect metadata.
Creating a backup job by selecting the virtual machine directly constitutes an agent-based backup.