You can change the amount of memory resources allocated to a virtual machine by using the shares, reservations, and limits settings.

A virtual machine has three user-defined settings that affect its memory resource allocation.
Places a limit on the consumption of memory for a virtual machine. This value is expressed in megabytes.
Specifies the guaranteed minimum allocation for a virtual machine. The reservation is expressed in megabytes.
Each virtual machine is granted a number of memory shares. The more shares a virtual machine has, the more often it gets a time slice of a memory when no memory idle time is present. Shares represent a relative metric for allocating memory capacity. For more information about share values, see the vSphere Resource Management documentation.

Assigning a virtual machine a reservation larger than its configured memory is wasteful. The vSphere Client does not allow you to make such an assignment on the Resources tab. If you give a virtual machine a large reservation and then reduce its configured memory size on the Hardware tab, the reservation is reduced to match the new configured memory size. You must power off the virtual machine before configuring memory resources.

Note: Virtual machine hardware versions 9, 10 and 11 features are read-only when connected to the ESXi host or vCenter Server system using the vSphere Client.


  1. In the vSphere Client inventory, right-click the virtual machine and select Edit Settings.
  2. Click the Resources tab and select Memory.
  3. Allocated the memory capacity for this virtual machine.
    Option Description
    Shares The values Low, Normal, High, and Custom are compared to the sum of all shares of all virtual machines on the server. You can use share allocation symbolic values to configure their conversion into numeric values.
    Reservation Guaranteed memory allocation for this virtual machine.
    Limit Upper limit for this virtual machine’s memory allocation.
    Unlimited No upper limit is specified.
  4. Click OK to save your changes.