Sub-Capacity on Ineligible Technology: The Hidden Disqualifier

Sub-capacity licensing only applies on eligible virtualization technology. Run the same workload on an ineligible hypervisor or operating system and IBM charges full capacity, regardless of how few cores you actually use. This is one of the most expensive surprises in an audit.

The eligibility rule most buyers miss

Sub-capacity is a privilege with conditions, not a default. IBM publishes which virtualization technologies are eligible for sub-capacity and under what rules. Software running on an eligible, correctly measured environment can be licensed to the virtual cores it uses. Software running on anything outside that list is charged at full capacity, meaning every physical core in the host, even if the workload touches only a handful.

What counts as ineligible

Ineligible technology includes virtualization or operating environments not on IBM's eligible list, and older platforms that were never approved for sub-capacity. The classic example is an outdated server operating system that has dropped off the eligibility list. The workload still runs, but the licensing basis silently reverts to full capacity.

The full-capacity default

The financial gap is large. Consider WebSphere using 4 of 32 host cores. On an eligible, correctly measured environment that is 480 PVU at sub-capacity. On ineligible technology it becomes the full 32 cores, roughly 3,840 PVU, an eightfold increase for the identical workload. Multiply that across an estate and a quiet eligibility gap becomes a seven figure finding.

LPAR, VMware and cloud differences

Eligibility and counting rules differ by platform. On Power LPAR, IBM counts the cores allocated to the partition even when they sit idle, so an oversized allocation inflates the count. VMware, Hyper-V and public cloud each carry their own eligibility conditions and measurement rules. Assuming one platform's rules apply to another is a common path to an ineligible position.

How to find ineligible technology before IBM does

The defense is an estate map that lists every IBM workload, the platform it runs on, and that platform's current eligibility status, reconciled against ILMT. Where a workload sits on ineligible technology, you have two buyer side options: move it to an eligible, measured platform, or size the full-capacity exposure deliberately and plan for it. Either way, finding it first means you control the remedy instead of inheriting a finding.