AIX on Power Systems is licensed by processor entitlement against the active LPAR or partition. Capacity on demand, micropartitioning, and PVU rules drive the real cost. This guide unpacks the mechanics and the procurement playbook.
IBM Power and AIX licensing turns on processor entitlements, capacity on demand activation, and micropartitioning rules, and the buyer who reads the LPAR map controls the bill.
AIX and Power software license to activated processor cores, translated into Processor Value Units for many IBM programs. The activated footprint drives the bill.
The licensable unit is the activated core, not the installed core. Review the entitlement basis on the IBM Power page and the AIX page.
Capacity on demand lets you activate cores temporarily. Those activations can raise the licensable footprint if you do not track them.
Deactivate cores you no longer need, and confirm how temporary activation interacts with your entitlements. IBM documents sub capacity terms on its sub capacity licensing page.
IBM Power licensing posture and exposure
| Posture | Requirement | Cost impact |
|---|---|---|
| Full capacity | No tooling needed | Highest cost |
| Sub capacity | ILMT deployed | 20 to 40 percent lower |
| Shared pool cap | Pool configured | 15 to 30 percent lower |
| CoD untracked | Activation logging | Avoidable overage |
Micropartitioning with shared processor pools can cap the cores a partition may consume, which caps PVU exposure.
A capped shared pool limits the maximum cores a set of partitions can use, so you license the cap rather than the whole server. Configured well, this is one of the largest savings.
Sub capacity is the right posture for most estates, and it requires the IBM License Metric Tool. Full capacity is the expensive default you adopt by omission.
The common advice is that AIX and Power licensing is fixed by the hardware you bought, so there is little room to optimize. We disagree. In roughly 13 of the 25 Power estates Morten Andersen reviewed in 2024 to 2025, the licensable cost was set by configuration choices, capping shared processor pools, deploying ILMT for sub capacity, and deactivating unused capacity on demand cores, rather than by the box itself. Buyers who treated the LPAR map as a cost lever cut PVU exposure by 15 to 40 percent. The buyer side move is to license the configuration you actually run, not the capacity the server could theoretically deliver.
Source: Redress Compliance advisory engagement file, 2024 to 2025.
On Power you do not license the server you bought. You license the configuration you run, if you build it that way.Morten Andersen, Co Founder, Redress Compliance
A buyer side reference on IBM audit posture, ILMT compliance, PVU reconciliation, subcapacity rules, and the protective contract clauses that hold the deal through the term.
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Open the Paper →AIX licensing rewards careful baselining. Every refresh and every renewal is the opportunity to rebaseline the entitlement against measured workload. Most AIX customers find ten to thirty percent of entitlement is unused in production. That headroom is the negotiation lever.
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AIX and Power software license to activated processor cores, which translate into Processor Value Units for many IBM programs. The activated footprint, not the installed core count, determines the licensable cost.
Sub capacity licensing lets you license a partition rather than the whole server, which requires the IBM License Metric Tool to be deployed and reporting. It is typically 20 to 40 percent cheaper than full capacity.
Full capacity licensing requires you to license every core in the physical server regardless of how many a partition uses. It is the default that applies when ILMT is not deployed, and it is the most expensive posture.
Capacity on demand activations can raise the licensable footprint while they are active. If unused activations are left on, you may license more cores than the workload needs, so track and deactivate them.
Micropartitioning divides physical processors into shared logical partitions drawn from a processor pool. A capped shared pool limits the cores those partitions can consume, which caps PVU exposure and lowers cost.
You need the IBM License Metric Tool to qualify for sub capacity pricing. Without ILMT reporting in force, IBM expects full capacity licensing, which is the more expensive default for most estates.
A capped shared processor pool sets the maximum cores a group of partitions can use, so you license the cap rather than every core in the box. Configured well, this cut PVU exposure by 15 to 30 percent in our reviews.
Review Power licensing alongside any hardware refresh and at least once a year. Configuration drift, idle capacity on demand cores, and pool changes all move the licensable cost between reviews.
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