I had 1 GB of RAM when I installed the virtual machine. So I assigned 512 MB to the Virtual machine. Recently I added 2.5 GB of RAM. Tried to increase the RAM size of the VM. But the location of the RAM size is grayed out. I did reboot the VM but still the location is grayed out. Anybody there can help?
As written you have to power-off a VM to change vRAM (or vCPU) settings.
With vSphere Advanced (or more) and SOME guest OS you can use the hot-add feature. But you must enable this feature at VM level when the VM is powered off.
You must enter in your guest OS and make a shutdown from there.
Or, if you have VMware Tools installed, use guest shutdown.