When a new version of a product is released, the older versions are no longer available for purchase. Downgrading a license key allows you to use an older version of a product. If you downgrade a license key, you can revert to the newer version by upgrading the license key.
For more information, see Upgrading license keys in My VMware (2006974).
Only Super Users, Procurement Contacts, and users with Upgrade & Downgrade License Keys permissions can downgrade a license key.
Not all products are eligible for downgrade. When you select Downgrade License Keys from the I want to drop-down, you only see products that can be downgraded.
- The downgrade option is not available for ESXi 4 Single Server to ESXi 3.x.
- The downgrade option is not available for vSphere Essentials to VI3.
- For licenses downgraded to ESX 3.x or Site Recovery Manager 1.x, the original licenses are not decreased or affected and the downgrade process cannot be reversed.
- Workstation 8 licenses can be downgraded to Workstation 7.x licenses.
- Site Recovery Manager 5 has two different editions: Standard and Enterprise. You can downgrade the Site Recovery Manager 5 Enterprise licenses, but you cannot downgrade Site Recovery Manager 5 Standard licenses.
Version Comparison Chart
This post has been written so I and others can start to understand vSphere licensing
Comparison of vSphere 5 Editions
VMware vSphere 5 licensing
vSphere 5 will be licensed on a per processor basis with a vRAM entitlement. Each vSphere 5 processor license will entitle the purchaser to a specific amount of vRAM, or memory configured to virtual machines. The vRAM entitlement can be pooled across a vSphere environment to enable a true cloud or utility-based IT consumption model. Just like VMware technology offers customers an evolutionary path from the traditional datacenter to a cloud infrastructure, the new vSphere 5 licensing model allows customers to evolve to a cloud-like “pay for consumption” model without disrupting established purchase, deployment, and license management practices and processes. Unlike vSphere 4.x licenses, vSphere 4.x licenses, vSphere 5 licenses do not impose any limits on the number of cores per processors and maximum size of RAM capacity per host
A diagram showing licesning changes between vSphere 4.x and vSphere 5.x