Are you just talking about alocating 4GB of memory, or are you trying to set a reservation of 4GB? I don't know why it would block you from allocating 4GB even if you didn't have that much physical memory available, it should allow you to overallocate.
Are you getting some kind of error?
Thanks for the reply
no - I can't allocate more than I've already done and get it to work
I can allocate a bit more - but that appears to be taking it out of the hypervisor's overhead and I get some generic error message about it not being able to start the virtual machine.
I know I can't allocate the virtual machine all 4Gb - but I should be able to allocate it 3Gb or 3.5Gb shouldn't I?
It would appear that although the hypervisor knows there's 4Gb of RAM there - it's only using / allocating 2Gb