Processor Value Units sit at the heart of IBM software licensing. This buyer side guide covers PVU math, sub capacity rules, the ILMT obligation, audit defense, and the PVU to VPC transition reshaping the IBM portfolio.
Processor Value Units price most IBM software by core, scaled by chip type, and your sub capacity savings live or die on ILMT reporting filed on time.
A Processor Value Unit is IBM's per core capacity unit. Each physical core is assigned a PVU rating set by processor family, then multiplied by the cores running the software. Most cores rate 70 to 100 PVUs.
The rating table is published in the IBM Passport Advantage documentation. You count cores, apply the rating, and license the total. Counting the wrong cores is the most common starting error.
You license the cores where the software can run, not where it happens to run today. On a cluster, that distinction is the whole ballgame, and it is why sub capacity rules and ILMT matter so much.
Sub capacity licensing lets you license the virtual cores allocated to the software rather than every core in the host or cluster. The savings are real, often 40 to 70 percent, but they are conditional. The conditions are set out in IBM's sub capacity terms.
Miss a condition and IBM reverts the affected product to full capacity. That means licensing every core in the environment, which is where the 8 to 15 times multiplier comes from.
PVU exposure by licensing basis
| Scenario | Licensed cores | Relative PVU cost |
|---|---|---|
| Sub capacity, ILMT current | Virtual cores allocated | Baseline |
| Sub capacity, ILMT lapsed | All cluster cores | 8 to 15x |
| Full capacity, no virtualization | All physical cores | 4 to 8x |
| Capped partition, ILMT current | Capped vCPU | Baseline or lower |
The IBM License Metric Tool is the evidence that earns sub capacity pricing. Without current ILMT data, IBM's default audit position is full capacity. The tool and its obligations are documented in the ILMT product documentation.
An IBM audit almost always opens with an ILMT data request. The auditor compares discovered deployment against entitlement. Gaps in coverage, not overuse, drive most findings.
The exposure is rarely a license you forgot to buy. It is an agent that stopped reporting on a host that kept running the product. Find those gaps before the auditor does.
The standard reseller pitch is that converting everything to VPC and trusting ILMT to run itself solves PVU risk. We disagree. In roughly 30 to 45 IBM estates we reviewed, the savings sat in two places the pitch ignores. First, ILMT coverage gaps quietly reopened full capacity exposure on 20 to 35 percent of servers while everyone assumed the tool was fine. Second, blanket VPC conversion locked in cost on stable workloads that were cheaper to leave on PVU for one more cycle. The buyer side move is to audit ILMT coverage first, then model conversion product by product, rather than treating either as a default.
Source: Redress Compliance advisory engagement file, 2024 to 2025.
The IBM audit opened with an ILMT data request. We ran a pre audit health check, fixed three agent gaps, and reconciled entitlement to deployment. The full capacity exposure dropped from twelve million to under two before settlement.
IBM is migrating most Software Group products from PVU to Virtual Processor Core through 2027, a shift visible across the IBM software catalog. VPC tracks allocated virtual cores and is simpler to manage on virtualized estates.
Conversion is not automatic and it is negotiable. The right move is to model TCO product by product before agreeing to convert, because some stable workloads cost less on the old PVU basis for one more cycle.
Stacked IBM and Red Hat OpenShift deployments track separate metrics. Run both reports monthly and reconcile each at renewal so neither slips into a default position.
Many products do, but not all. Some IBM products use named user, authorized user, RVU, or per server metrics. The PVU model covers most IBM Software Group products that run on processors. The buyer side review confirms the metric on every product before counting.
The default audit position becomes full capacity for the lapsed period. The financial exposure can be 8 to 15 times the sub capacity number on the affected products. Recovery requires ILMT redeployment with retroactive reports, which IBM auditors sometimes accept and sometimes do not.
Not automatically. Most enterprises convert on the next renewal cycle because VPC is simpler to track. The defended position picks the conversion that lowers TCO product by product. Some products on stable hosts cost less staying on PVU for one more cycle.
Rates are set centrally by IBM and rarely move. The negotiation lever sits in the PVU quantity instead. Sub capacity application, deployment reduction, and shelfware drops are the available levers, and a VPC conversion can reset the pricing baseline.
Most enterprises will during the transition years. The two metrics track separately. ILMT continues to manage the PVU products while VPC products track in your SAM tool. Run both reports monthly and reconcile at renewal time.
Audit clauses typically allow a look back across the current term and sometimes prior terms. The practical limit is your records. Keeping two years of ILMT reports gives you the evidence to defend the sub capacity position.
OpenShift uses its own core based subscription metric, separate from Passport Advantage products. ILMT may discover OpenShift but the licensing tracks independently. Enterprises running both reconcile each metric on its own schedule.
Before an audit notice and before a renewal quote. A clean baseline built in calm conditions is worth far more than a scramble under an audit clock. Most engagements deliver the first 10 to 20 percent inside three months.
A buyer side framework for ILMT compliance, the PVU baseline, and the VPC transition. Includes the ILMT health check template, the entitlement reconciliation worksheet, and the conversion map used across hundreds of IBM engagements.
Independent. Buyer side. Built for CIOs and procurement leads carrying IBM software estates or facing an IBM audit. No vendor influence. No sales kickback.
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