IBM has offered the IBM License Metric Tool (ILMT) for years. With ILMT installed, clients can license their server-based software with the PVU metric by the sub-capacity method (only license the virtual cores allocated).
Occasionally, someone claims they can’t install ILMT because they missed the initial 90-day window IBM grants in the IBM Passport Advantage Agreement (IPAA).
Although that is in the IPAA, why can’t you install ILMT now?
If you install ILMT by the end of 2017, by 2019 you’ll have two years of quarterly reports and comply with IBM’s sub-capacity licensing terms.
If you don’t install ILMT, your licensing is calculated using the Full Capacity methodology by default. Full Capacity is the entire processing power of the physical host server. With environments becoming increasingly virtualized, besides the use of cloud, it’s in your best interests to license by Sub Capacity by meeting IBM’s requirement for quarterly ILMT reports.
How big a deal is the difference between Sub and Full Capacity?
If I had a large p795 with 256 cores, it could be huge. Here is an example using WebSphere Application Server (WAS) and MQ running on the same frame:
- Full Capacity: If MQ and WAS were both installed on this frame, they’d both need 30,720 PVUs of licenses each
- Sub Capacity: If only one 2-core LPAR had MQ, Sub Capacity would be 240 PVUs. The two LPARs of WAS total 3 vCPUs or 360 PVUs of licensing.
Outside of IBM hardware, the licensing difference between Full and Sub-Capacity can also be a large quantity.
If I had some 2-socket blade servers in a cluster the impact may not seem as bad, but due to the possibility that every virtual server could be on a separate physical host, the Full Capacity calculation may be larger than expected.
Here is an example of the physical hosts in the cluster, along with the PVU calculations for each:
If I had five virtualized servers within that cluster, all with small allocated vCPUs, one might assume that only 490 PVUs were required. However at Full Capacity, the licenses required would be 4,480 PVUs.
If ILMT is not installed now, when will it be installed? If you never install ILMT, your environment will remain at Full Capacity under IBM’s current IPAA rules.