HP Instant Capacity User's Guide for versions 8.x > Chapter 4 Using Instant Capacity to Manage Processing Capacity

Activating Cores

  Table of Contents


The icapmodify command provides the ability to increase processing capacity instantly by activating cores with available usage rights in nPartitions (hard partitions) of Instant Capacity systems. At any time, any number of inactive cores with usage rights can be activated, as long as sufficient usage rights are available. See “Instant Capacity Integration with Virtual Partitions (HP-UX only)” for details about activation in virtual partitions.

Activating Cores in nPartitions

The software provides two types of activation:

  • Instant ( icapmodify command’s default behavior) — the activation occurs immediately

  • Deferred ( icapmodify command’s -D option) — the activation occurs after the next reboot of the partition

Instant activation of cores occurs when the icapmodify command is used with either the -a or -s option, and the -D option is not specified.

Deferred activation of cores occurs when the icapmodify command is used with both the -D option and either the -a or -s option specified. With the deferred option (-D), core activation occurs after a reboot of the partition. The scheduled timing of the reboot (and the core activation) can take place at a planned time. For example, if you activate cores in deferred activation mode and schedule a partition reboot to occur on the first day of the next month, the cores are activated at that time.

IMPORTANT: If you shut down a partition for 24 hours or more, you should also power it off to avoid additional charges. To power off the partition, execute the PE command from the system MP.

On HP-UX systems, always use the shutdown command when shutting down or rebooting an Instant Capacity partition. See the HP-UX manpage shutdown(1M) for information on the shutdown command.

On OpenVMS systems, always use the sys$system:shutdown.com procedure when shutting down or rebooting an Instant Capacity partition.

On OpenVMS iCAP systems, HP strongly recommends that you activate cores using the icapmodify or the ICAP SET command. The use of the START CPU command on an iCAP system may result in unintended consequences, such as a reduction of available temporary capacity. Another unintended side effect may be the adjustment in core usage across the complex depending on the intended core settings on the partition where the START CPU command was issued.

Deferred activation does change the quantity of activated and inactivated processing capacity, even if the partition reboot has not yet occurred. Compliance checking is calculated as if the activation had not been deferred.

To activate one or more inactive cores, use the icapmodify command as root. See the HP-UX manpage icapmodify(1M) for details.


The Instant Capacity software will not activate a core that is marked for deconfiguration. Also, you cannot use Instant Capacity to activate more cores than are configured in the current nPartition. If you want more, you need to modify the nPartition with the parmodify command. You can use Instant Capacity to activate more cores than are configured into the current virtual partition, but only if the associated nPartition contains enough unassigned cores to fulfill the request. Otherwise, you need to use parmodify to reconfigure the nPartitions, or vparmodify to remove cores from other virtual partitions within the same nPartition (essentially, adding to the unassigned pool).

Instant Capacity Activation Example Session

The following example shows you how to activate an additional core. At the beginning of this activation session, there are a total of 4 cores in the partition; 2 cores are activated and 2 are inactive, but usage rights have been acquired to activate at least one inactive core. In this example, 1 additional core is activated, leaving the partition with 3 active cores and 1 inactive core:

Example 4-3 Activating an Additional Core (HP-UX)

/usr/sbin/icapmodify -a 1 "Add CPU for new FY: Bill P."

3 cores are intended to be active and are currently active.

Points of interest in the above activation example are:

  • The core activation is instant (that is, a reboot is not required).

  • The double-quoted text serves as an audit trail of why the activation was done and who performed it. This information is optional and is written to the Instant Capacity log file (var/adm/icap.log) if provided.

NOTE: To defer the activation until the next reboot, add the -D option to the command. See the HP-UX manpage icapmodify(1M) for details.

The icapmodify command allows you to activate additional cores with the -a option, or set the total number of active cores with the -s option. For example, the icapmodify command/option -a 2 activates two additional cores in a partition. The icapmodify command/option -s 2 sets the total number of active cores in a partition to 2.

See “Software Application Considerations” for details of software application implications when activating additional cores.