Below is an example of ovm_vmdisk usage. It shows a virtual machine with three disks, each attached in a different way:

# ./ovm_vmdisks -u admin -p password -h localhost -v MyVM01 
Oracle VM Retrieve Disk utility 0.5.2.
Connected.
Virtual Machine : 'MyVM01' status : 'Running'.
Assigned Server : OVS_01
Virtual Disk : 'MyVM01_bootdisk' size : 20GB 
   file=/OVS/Repositories/0004fb0000030000b0272c74e714ab12/VirtualDisks/ \
   0004fb00001200006e548a28cb886f42.img
   mountpoint=/dev/mapper/3300000006160a212/VirtualDisks/ \
   0004fb00001200006e548a28cb886f42.img
Virtual Disk : 'MyVM01_datadisk' size : 250GB
   file=/OVS/Repositories/0004fb00000300005b06362f2d866a98/VirtualDisks/ \
   0004fb0000120000f217eb8c0fa70eef.img 
   mountpoint=nfs01:/mnt/vol2/repo03/VirtualDisks/ \
   0004fb0000120000f217eb8c0fa70eef.img
Physical Disk : 'pd003'
   device=/dev/mapper/3300000009b7b2cc4
Config File :
   file=/OVS/Repositories/0004fb00000300005b06362f2d866a98/ \
   VirtualMachines/0004fb00000600008757e38248a544e6/vm.cfg
   mountpoint=nfs01:/mnt/vol2/repo03/VirtualMachines/ \
   0004fb00000600008757e38248a544e6/vm.cfg

As you can see in the console output, VM 'MyVM01' is currently running. Note that backing up a running VM would be inconsistent, therefore it is highly recommended that you shut down the VM prior to making any backups. The console output shows that the virtual machine contains three disks, two virtual and one physical, and also provides the location of the virtual machine configuration file: