IBM Sub-Capacity Licensing and ILMT: A Plain-Language Guide
IBM sub-capacity licensing explained in plain language: PVUs, full vs sub-capacity, the ILMT requirement, quarterly reports and how to stay eligible.
By the MI Solutions SAM team9 min read2 exhibits
Many IBM products are licensed by processor capacity, measured in Processor Value Units (PVUs). In a virtualized environment you can usually license only the capacity available to the virtual machines running IBM software, which is called sub-capacity licensing, instead of the full capacity of the physical server. The saving can be large. The condition is strict: you must run IBM License Metric Tool (ILMT) correctly and keep its reports.
Full capacity vs sub-capacity
Exhibit 1
In this example, sub-capacity licensing needs one-eighth of the PVUs. Across an estate with dozens of virtual machines on large hosts, the difference can be the largest single number in the IBM relationship. That is why staying eligible matters so much.
What ILMT requires
To remain eligible for sub-capacity licensing, organizations generally need to:
ILMT obligations
Exact obligations are set out in IBM's Passport Advantage terms; check them for your agreement.
Exhibit 2
Where organizations go wrong
01Incomplete coverage
ILMT not installed on every relevant server, or agents not reporting.
02Missing reports
Reports not produced every quarter, or not retained.
03Wrong bundling
Software components counted as separate products instead of parts of the product you own.
04New hosts
Virtualization hosts added without ILMT coverage.
How MI One helps
Frequently asked questions
Is ILMT free?
IBM provides ILMT to eligible customers at no additional license charge, but deploying and maintaining it takes effort.
What happens if ILMT reports are missing?
IBM may assess licensing at full capacity for the affected period, which can be far more expensive.
Who should own ILMT?
Usually the infrastructure team runs it, with the SAM function reviewing bundling and signing off the quarterly reports.
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