You can upgrade the vCloud Usage Meter appliance by using an .iso image that includes a complete Photon OS update.

You can install vCloud Usage Meter 4.6 as an in-place upgrade on top of vCloud Usage Meter 4.3 and later.

If you want to upgrade from vCloud Usage Meter 3.6.x, you must install vCloud Usage Meter 4.6 as a new appliance.
Note: To ensure the automatic aggregation and reporting of the monthly product consumption data, after a successful upgrade to version 4.6, VMware recommends that you do not revert to the snapshot of the source vCloud Usage Meter appliance.

If you want to run in parallel both old and new appliances for a full reporting period, set the vCloud Usage Meter 4.6 instance to Test mode. You can still collect, aggregate, and reference the product consumption data from the vCloud Usage Meter 4.6 instances. For more information, see the https://kb.vmware.com/s/article/82529?lang=en_US KB.

Then if you want to activate vCloud Usage Meter 4.6 for reporting, through the VMware Cloud Services Console, update the mode of the vCloud Usage Meter 4.6 instance from Test to Production.

To upgrade the vCloud Usage Meter appliance, you must install only the official vCloud Usage Meter updates that VMware provides.