Below are some of the most frequently asked questions about Sub-capacity licensing.

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1. What is sub-capacity (virtualization) licensing and how is it different from standard licensing?

Sub-capacity licensing lets you license a core-based software program for less than the full processor core capacity of the server, when the software program is deployed in an eligible virtualization environment. With full capacity licensing, customers are required to obtain license entitlements for all activated processor cores in the server, regardless of how the software was deployed.

IBM’s Passport Advantage Sub-Capacity Licensing offering

enables customers to license software for only the processor core capacity available to the partition hosting the IBM software

provides a tool (ILMT) which allows the customer to track and manage the processor core capacity available to IBM core-based software

2. What is virtualization licensing and how does it relate to sub-capacity licensing?

Recognizing that the use of the word “virtualization” has become commonplace in the industry, IBM will sometimes refer to its "Sub-capacity” offering as “Virtualization Capacity” or "Virtualization Licensing". You should expect these names to be used interchangeably. For the purposes of licensing, containerization is considered separately..

3. What is full capacity licensing and how does it relate to sub-capacity licensing?

Full capacity licensing is based on every physical, activated processor core in the physical server. Back when servers were one processor core sitting on top of one chip plugged into one socket, software was licensed on full capacity basis by default. The concept of full capacity licensing has not changed, even with the proliferation of multi-core and multi-socket servers. Licensing was basically simple. But with partitioning and more sophisticated server virtualization technologies that create virtual CPUs, virtual servers/partitions (aka virtual machines, LPARs, etc.) that can be moved and/or resized on the fly, came the demand for more flexible licensing terms. Thus IBM announced its sub-capacity licensing offering back in 2005. Today, IBM has the broadest support of virtualization technologies in the industry, including RISC and x86 platforms, and Linux on System z. In addition we are the only vendor which provides a tool to assist customers in maintaining compliance.

4. Is a tool currently required to track sub-capacity license use?

Yes, the use of IBM License Metric Tool is required for sub-capacity licensing. IBM also allows clients to make use of additional approved tools. See the ILMT webpage for more information about these tools.

5. Are customers required to report their license deployments to IBM?

Customers must maintain documentation as evidence of on-going license compliance management of capacity available to IBM software. As per the terms of the offering, customers must make these reports available upon IBM request (refer to the IBM Passport Advantage Agreement).

6. What software metrics are eligible to license under sub-capacity licensing?

IBM support all software products that use core-based pricing metrics:

  • Processor Value Unit (PVU)
  • Virtual Processor Core (VPC)
  • Resource Value Unit: Managed Activated Processor Core (RVU MAPC)

7. How can I determine if a product is licensed based on PVU/VPC/RVU MAPC?

The product and/or part number description will almost always state the licensing metric. The following links are sources for Passport Advantage pricing/licensing:

IBM License Information document database

IBM Passport Advantage Licensing

8. What is the algorithm for determining "sub-capacity pricing"?

IBM licenses on the basis of whole processor cores, based on the lower of the physical or the virtual cores. The minimum requirement for software licensing is the appropriate number of license entitlements for one processor core. This licensing is based on the processing capacity available to the IBM software. IBM licenses to the lower of the sum of virtual capacity or the full (physical) capacity of the server. Reference the Virtualization Licensing Counting Rules for details and examples on calculating sub-capacity license requirements in various scenarios.

9. Can we license entitlements for one processor core in a server, for all eligible virtualization environments?

10. Can we license entitlements for less than one processor core in a server, for all eligible virtualization environments?

No. The minimum requirement for software licensing is the appropriate number of license entitlements for one whole processor core.

11. How many license entitlements are required for a virtual machine (VM) in a VMware virtualization environment?

Licensing is based on the processing capacity available to the IBM software. In the case of VMware, we license based on the number of  virtual cores  (vCPUs in VMware terminology) available to a partition. Each vCPU is equal to one processor core for licensing. We license to the lower of the sum of vCPUs or full (physical) capacity of the server.  For additional details, view Counting Software licenses using specific virtualization technologies on the Sub-Capacity website.

12. How many license entitlements are required for a partition in an eligible PowerVM virtualization environment?

Licensing is based on the processing capacity (expressed in PVUs) available to the IBM software. In the case of a PowerVM partition we license based on the virtual processor core capacity available to a partition depending on the partition mode (capped or uncapped).

In the case of a certain partitions (capped partitions) that have a fractional core processing capacity, we aggregate fractional processor cores, apply shared pool capping rules, and round up at the server level to the next whole processor core. IBM licenses to the lower of the sum of virtual cores or the full (physical) capacity of the server

For additional details, find the scenario that best depicts your situation by going to:
Scenarios for Power Systems available from Counting Software licenses using specific virtualization technologies.

13. Why are some core-based products ineligible for sub-capacity licensing?

For those few exceptions, the products are typically not capable of being deployed in a virtualized server environment, the product is always deployed on the entire server environment, or the product solution's architecture is such that ILMT is unable to discover the processor core capacity of the virtualized server environment. These products must be licensed on a full capacity basis. See the Passport Advantage Sub-capacity Licensing Eligible Products.

14. Is sub-capacity licensing available for both Passport Advantage and Passport Advantage Express customers?


15. How do customers enroll in the Sub-capacity Licensing program?

Sub-capacity licensing terms are included in the IPAA. Visit Passport Advantage for more details.

16. If a customer has a 16-processor core server, but only 8 cores have been activated, is this sub-capacity?

No. Full capacity licensing requires the customer to only acquire licenses for the 8 activated cores in this situation. As more processors are activated, the customer needs to acquire additional software license entitlements. Sub-capacity will only apply if the customer sets up partitions that have less than 8 active processor cores available. See the next FAQ below for more information on activated processor cores.

17. Are customers required to acquire license entitlements for deactivated processor cores on a server?

No. IBM only requires licenses for activated processor cores. Some servers may be delivered with one or more processor cores deactivated, or turned off, to allow for future system growth. For instance, a system may ship with 8 physical processor cores where only 6 have been activated. This would allow the customer to have the additional 2 processor cores turned on in the future as their workload requirements grow. For software that is licensed on a per core basis, this server only contains 6 activated processor cores. Clients would only be required to obtain software licenses for all activated processor cores available for use on the server, so in this example, licenses are not required for the remaining 2 cores until they are activated.

Activated processor cores are physical processor cores that are available for use in a server. They include processor cores:

In summary, additional licenses are required at the time any additional processor cores are activated.

18. If mobility is employed in a virtual environment (e.g. Power Live Partition Mobility, Vmotion), are virtual cores counted each time they move to a new server?

No. Virtual cores in a virtual machine (VM) that has moved as a result of a mobility event will not be counted more than once. The same VM may not run on two servers simultaneously.

19. How and when will the number of eligible environments be expanded?

Since the inception of the Passport Advantage Sub-Capacity offering, IBM has continually made new server virtualization technologies eligible to participate in this flexible option. Given the fast changing virtualized server technology market, in order to be notified when IBM License Metric Tool support for additional eligible virtualization technologies become available, customers will need to subscribe to "My Notifications" (instructions are in a separate FAQ below). They should also monitor the Eligible Virtualization Technology exhibit for additions.

20. How long do customers have to install ILMT?

New sub-capacity customers are required to implement IBM License Metric Tool (ILMT) within 90 days of their first Eligible Sub-Capacity Product deployment on an Eligible Virtualization Environment.
Existing sub-capacity customers should promptly upgrade to new versions, releases or modifications when they are made available per the terms of the IPAA.

21. What are the exceptions to the requirement to use ILMT for sub-capacity licensing?

With the release of IBM Passport Advantage Agreement v11, IBM will no longer be supporting exceptions for sub-capacity reporting requirements. Clients may continue to manually report sub-capacity deployments until January 1, 2024 if they were, prior to May 1, 2023, manually reporting on an exception basis and meet the requirements outlined in IBM Passport Advantage Agreement v10. Please see the IBM License Metric Tool for more information.

22.What if ILMT doesn't support my virtualization technology?

With the release of IPPA v11, manual exceptions are no longer accepted. Unsupported technologies must be accounted for via Full Capacity licensing. If you wish to take advantage of sub-capacity licensing, you must use a supported virtualization technology. If you were previously eligible to report manually, until January 1, 2024, you may refer to the guidance for your eligible virtualization technology and manual tracking spreadsheet example available from Sub-capacity webpage.

23. Is ILMT mandatory for Sub-capacity licensing?

All clients must use an approved and validated tool for metering core-based software usage. ILMT is the standard tool offered and maintained by IBM. However, customers may use alternative tooling as referenced on the Sub-Capacity and ILMT webpages.

24. For a customer who qualifies for an ILMT exception and is doing manual tracking/reporting, what tools can the customer use to supplement manual efforts?

For those who made use of reporting exceptions prior to May 1, 2023: the announced exceptions to the ILMT requirement, the manual counting/reporting requirement can be supplemented by alternative tools if they assist in an accurate measure of the peak core capacity by software product. There are several products in the marketplace that can perform simple software inventory scans and even fewer solutions exist that can determine the type of processor core on the hardware server (a requirement to determine the number of entitlements to be licensed). But unlike ILMT, these tools are unable to provide on-going monitoring of changes to the processor core capacity of a virtualized partition, to capture the maximum (peak) capacity available to the IBM core-based software

Even ILMT can be used in unsupported, yet eligible server virtualization technology environments to assist in capturing the servers' basic hardware processor core and software inventory information -- but if ILMT doesn't support the virtualization technology, it will not generate the correct answer for partitions, LPARs, VMs, domains, etc. That data must be captured manually using whatever means provided by the operating systems, virtualization technologies, change management logs, etc.

25. What selection do I make under IBM's My Notifications in order to be notified when ILMT updates become available?

After logging in with your IBM ID, in the Product lookup bar input: IBM License Metric Tool, then click on 'Subscribe'. If you do not have an IBM ID, visit My Account Profile.

26. What should be ILMT's default reporting period?

The Sub-capacity terms reflect quarterly reporting as the maximum amount of time allowed before having to analyze and reconcile ILMT reports. Most customers will probably need to perform this effort on a monthly basis. Some customers, with very dynamic server environments, where partitions are resized/moved frequently and/or with changes in their software inventory, may need to create weekly reports in order to keep up with the volume of change. Only customers with the most stable of virtualized server environments would be able to maintain compliance with IBM licensing terms by doing quarterly reports.

27. Where can I find general information to learn more, additional FAQs specific to ILMT, examples of the reports available and additional ILMT support?

Refer to the ILMT Documentation website for more technical information and resources.

28. Is it necessary to have ILMT on disaster recovery back-up servers to monitor the processor core capacity required for licensing terms?

Yes, you should install agents on any backup server where ILMT is also installed on the primary server/partition.

You can then exclude such instances from calculation if a license is not required (typically warm/cold back-ups, but the license requirement can vary by product). For specifics, refer to the product's announcement letter [by searching the Offering Information page] or the product's License Information Document [by conducting a Software license agreements search].

29. Where should ILMT Agents be installed?

ILMT agents must be installed on an Eligible Virtualization Environment hosting Sub-capacity Eligible Products. Additionally, for some virtualization technologies, agents need to be installed on system hosting virtual machines.

Infocenter topic for agent installation

30. How can a customer obtain the IBM License Metric Tool?

Even though ILMT is no-charge product offering, an order must be still placed to establish an IBM entitlement record for the license as well as software subscription and technical support* (S&S) coverage. That's because ILMT receives the same level of technical support offered for the rest of the Passport Advantage product portfolio, as opposed to other free tools and utilities that are offered "as-is" with limited to no technical support.

31. Why does a customer have to order ILMT? Why can’t they just download it?

Most simple download products provide little, if any, technical support - but provided on an "as-is" basis. IBM provides the same support for ILMT that we do for our other mission-critical software. So even though ILMT is a no-charge product offering, an order must be still placed to establish an IBM entitlement record for the license as well as software subscription and technical support* (S&S) coverage.

32. What is the part number used to order ILMT?

The initial order for ILMT should use P/N D561HLL. In order to maintain an entitlement record, S&S should renewed annually using P/N E027NLL. For additional guidance and instructions on ordering ILMT, see IBM License Metric Tool PA Online Ordering.

33. Why do I need to renew Software Subscription and Support for a no-charge product?

S&S renewal using P/N E027NLL is optional -- and is only required if the customer needs to be entitled to receive product updates/upgrades and technical support*. But note that keeping ILMT up-to-date is a requirement of the sub-capacity offering terms so S&S renewal would be a requirement for any customer required to use ILMT.