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

Deactivating Cores

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Deactivating Cores in nPartitions

You have the ability to decrease processing capacity instantly on HP enterprise servers with the Instant Capacity software (even on servers with sufficient usage rights such that all cores can be simultaneously active). Any number of active cores can be deactivated at any time, within the partition constraints listed below. Core deactivation can be useful for load balancing cores in nPartitions (hard partitions) of Instant Capacity systems. See “Instant Capacity Integration with Virtual Partitions (HP-UX only)” for details about deactivating cores in virtual partitions.

The software provides two types of core deactivation:

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

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

Instant deactivation of cores occurs when the icapmodify command is used with the -d option, and the -D option is not specified.

IMPORTANT: On OpenVMS iCAP systems, HP strongly recommends that you deactivate cores using the icapmodify or the ICAP SET command. The use of the STOP CPU command on an iCAP system may result in unintended consequences, such as a reactivation of the core when an Instant Capacity reconciliation transaction is requested.

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

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

Partition Constraints

An nPartition must have a minimum of one active core for each active cell. Deactivation of cores is limited by this rule. If the deactivation applies to a virtual partition, additional constraints may apply, such as the minimum number of cores specified for the virtual partition.

Deactivation Example Session for Hardware-partitionable Systems

The following example shows you how to deactivate an active core. At the beginning of this deactivation session, there are a total of 4 cores in the partition; 3 cores are active and 1 is inactive. In this example, 1 active core is deactivated, leaving the partition with 2 active cores and 2 inactive cores. As with activation, you do not specify a particular core to be deactivated. You specify only a number of cores to be deactivated.

Example 4-4 Deactivating an Active Core (HP-UX)

/usr/sbin/icapmodify -d 1

2 cores are intended to be active and are currently active.
NOTE: In the above deactivation example, the core deactivation is instant (that is, does not require a reboot). To defer the deactivation (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 deactivate cores with the -d option, or set the total number of active cores with the -s option. For example, the icapmodify -d 1 command/option deactivates 1 additional core in a partition. The icapmodify -s 2 command/option sets the total number of active cores in a partition to 2.