Demystifying ILMT: The Backbone of IBM License Compliance

04/17/2025|

When it comes to IBM software compliance, one tool stands at the center of it all: ILMT, the IBM License Metric Tool.

For many organizations, ILMT can feel like a black box—technical, confusing, and burdensome. But understanding how it works (and why it matters) is critical. In fact, your ability to use ILMT correctly could mean the difference between being compliant or facing a multi-million-dollar audit exposure.

In this post, we’ll demystify ILMT: what it is, how it works, and why it’s the backbone of IBM license compliance.

What is ILMT?

ILMT (IBM License Metric Tool) is a free IBM-provided tool designed to help organizations track software deployed on virtualized servers and measure the required Processor Value Units (PVUs) for compliance.

Why it exists:
IBM allows customers to license eligible products using Sub-Capacity (instead of Full Capacity) if they meet certain conditions—and ILMT is one of the biggest.

Without ILMT in place, you must license every core on the server where an IBM product is deployed, even if the software only uses a small portion of those cores.

Why ILMT Is So Important

Here’s why SAM professionals should care deeply about ILMT:

  1. It’s required for Sub-Capacity licensing.
    Without it, IBM defaults to Full Capacity licensing—which can double or triple your license exposure.
  2. It’s the only IBM-approved tracking tool (in most cases).
    While some exceptions exist (Flexera, BigFix Inventory with approval), IBM prefers ILMT by default.
  3. It provides auditable data.
    ILMT produces license usage reports that IBM accepts during audits—if configured and maintained properly.

 What ILMT Actually Does

  • Discovers IBM software across your virtualized environment
  • Identifies licensable products and their versions
  • Maps deployments to the underlying server hardware
  • Calculates PVU consumption based on IBM’s processor tables
  • Generates compliance reports (typically on a quarterly basis)

Common ILMT Mistakes (That Could Cost You)

  1. Not installing ILMT at all.
    If you’re using PVU-licensed products in a virtualized environment, this is a major red flag.
  2. Failing to generate and retain quarterly reports.
    IBM requires at least two years of ILMT reports as evidence. Without them, you risk being non-compliant.
  3. Improper configuration.
    If ILMT isn’t tracking all virtual machines, clusters, or hypervisors, your data is incomplete—and unusable.
  4. Not updating PVU tables or product catalogs.
    These updates are critical. They ensure ILMT reflects accurate processor values and recognizes the latest IBM software versions.
  5. Thinking ILMT is “set it and forget it.”
    ILMT requires ongoing monitoring, maintenance, and validation to stay compliant.

ILMT and Sub-Capacity Licensing: A Quick Primer

To qualify for Sub-Capacity licensing, IBM typically requires that:

  • The environment is eligible (virtualized, not cloud-native containers)
  • ILMT is deployed within 90 days of the first product installation
  • ILMT is properly configured and maintained
  • Quarterly reports are retained
  • You are not using an exempt environment (e.g., under 1,000 employees AND 1,000 devices—though even that has nuances)

Failing any one of these can trigger Full Capacity licensing by default.

What Does ILMT NOT Do?

  • It does not track entitlements. You still need to manually reconcile deployments with what you’ve purchased.
  • It doesn’t manage licensing for all IBM metrics—only those using PVUs or select VPC products.
  • It’s not plug-and-play—it requires coordination between IT, SAM, and sometimes vendors.

Tips for SAM Pros Managing ILMT

  • Schedule regular health checks to confirm ILMT is capturing all relevant systems.
  • Keep the PVU table and software catalog up to date—at least monthly.
  • Align your procurement records with ILMT data to build an accurate ELP (Effective License Position).
  • Document your reporting process to ensure continuity across audits and personnel changes.
  • Consider using BigFix Inventory if you’re already invested in BigFix—it builds on ILMT functionality and is IBM-approved.

Final Thoughts

IBM licensing is complex, but ILMT simplifies a big part of it—if you know how to use it. It’s not just a technical tool; it’s your first line of defense in managing IBM license compliance. When configured and maintained properly, ILMT can save your organization from unnecessary costs and audit risks.

Still unsure if your ILMT setup is compliant?

Let SoftCense help you turn ILMT from a compliance headache into a strategic asset.