I recently installed Oracle’s VirtualBox on Ubuntu, due to the fact that I needed to run Win7. I set the RAM to 1.5 GB for the virtual machine. My laptop has only 3 GB of memory, thus I should have another 1.5 GB for Ubuntu’s use.
Now, my question is: is the memory allocated for the VM usable when the VM is shut down?
Yes. It happen to Release the memory as soon as you close the Virtual box.
MoreDetails Look @:
https://forums.virtualbox.org/viewtopic.php?f=8&t=45385