License metric calculations in case of LPARs or VMs that are migrated between hosts

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The capacity scan runs every 30 minutes and is not synchronized on all computers. Lack of synchronization might impact license metric calculations in environments in which LPARs or VMs from a single host are migrated to another host. Because it is not possible to capture the capacity of all computers at the same time, software that is installed on an LPAR or VM that is migrated might be reported as running both on the old host and the new host at the same time. Such a situation might occur in case of technologies from which License Metric Tool retrieves capacity data by means of the capacity scan, not by using the VM Manager Tool nor the capacity scan of the virtualization host. Such technologies include, for example: Power Systems, System z, or Solaris.

Example

There is an environment in which two LPARs run on a physical host. IBM Db2 is installed on both LPARs. Each LPAR is assigned 10 cores. The value of license metric utilization for Db2 adds up to 20 VPCs. However, it is capped to 16 VPCs on the level of the physical host. As a result, license metric utilization that is reported for Db2 equals 16 VPCs.

Two LPARs running on a physical host

Both LPARs are migrated to a new physical host at the same time. However, because the capacity scan is not synchronized, it might report the first LPAR as still running on the old physical host and the second LPAR as already running on the new physical host. If such a situation occurs, license metric utilization that is calculated for Db2 is not capped and thus equals 20 VPCs.

The first LPAR running on the old host and the second LPAR running on the new host

Workarounds

You can use one of the following workarounds to avoid reporting higher license metric utilization.
  • Generate the audit snapshot and add a comment that the license peak was caused by the migration of a set of LPARs or VMs with the particular IBM software installed. Additionally, attach a snapshot generated a day before the migration, on the day of the migration, and a day after. It will ensure that it is visible that the license peak occurred due to the migration.
  • Reduce the capacity of the LPARs or VMs by at least 50%. This way, even if the capacity scan captures some LPARs or VMs as running on the old physical host and others as running on the new physical host, the sum of their capacity will not be higher than their normal capacity. To use this approach, perform the following steps.
    1. Reduce the capacity of the LPARs or VMs by at least 50%.
    2. Wait at least 30 minutes so that the reduced capacity is captured by License Metric Tool.
    3. Migrate the LPARs or VMs.
    4. Wait 30 minutes to ensure that the reduced capacity of the LPARs or VMs is captured by License Metric Tool.
    5. Increase the capacity of the LPARs or VMs to their original capacity.