The Tools.UpgradePolicy enumerated type defines when Tools are auto-upgraded for a virtual machine.
MANUAL : No auto-upgrades for Tools will be performed for this virtual machine. Users must manually invoke the Tools.upgrade operation to update Tools.
UPGRADE_AT_POWER_CYCLE : When the virtual machine is power-cycled, the system checks for a newer version of Tools when the virtual machine is powered on. If it is available, a Tools upgrade is automatically performed on the virtual machine and it is rebooted if necessary.
Enumeration: MANUAL, UPGRADE_AT_POWER_CYCLE,