HP Instant Capacity Version 10.x User Guide (762794-001, March 2014)

NOTE: Deferred activations and deactivations are not supported in any virtual partition
environment.
iCAP always consumes unused capacity before it consumes additional usage rights when activating
cores. iCAP always releases usage rights from unused capacity before it releases usage rights by
deactivating cores.
When to use the vparmodify or icapmodify commands
When usage rights freed by deactivating cores are to be used in a different nPartition, use the
icapmodify command. When usage rights freed by deactivating cores are to be used by another
virtual partition within the same nPartition, use the vparmodify command. The following sections
provide details on activating and deactivating cores within nPartition and virtual partition
environments.
What is unused capacity
In a virtual partition environment, the iCAP software may allocate or deallocate cores from what
is called “unused capacity”. Unused capacity is the difference between actual active and intended
active cores, and it is a side effect of using vparmodify to deactivate cores while not immediately
activating the cores in another virtual partition within the same nPartition. This is usually a transient
state, since a user typically migrates cores from one virtual partition to another with a deactivate
command followed by an activate command. However, unused capacity can persist if, for example,
a utility such as gWLM ignores an error status from an activation and leaves the previously
deactivated cores in an unassigned state. The iCAP software always takes unused capacity into
account when a request is made to activate or deactivate cores such that it attempts to eliminate
the discrepancy between intended active and actual active.
Static virtual partitions
If a virtual partition is static (that is, if its resources cannot be migrated, added, deleted, or modified)
and you attempt to activate or deactivate cores, the iCAP software displays a message indicating
that the configuration cannot be modified.
NOTE: The icapstatus command output indicates that the number of cores that can be assigned
(to the local virtual partition) is zero if the static resource attribute for the local virtual partition is
set.
Activating cores in a virtual partition environment
In a virtual partition environment, the icapmodify command must be used to modify processing
capacity when you make any adjustment to an nPartition or to multiple nPartitions. When you
execute the icapmodify command to activate a core, the iCAP software verifies that the request
can be satisfied. If so, the local nPartition’s intended active number is increased, and the appropriate
number of cores are added to the local virtual partition.
When cores in a virtual partition are activated using the icapmodify command, if unused capacity
is available, the cores are activated from the unused capacity balance before increasing the active
cores. If enough cores are available to meet the request, the proper number of cores are added
to the local virtual partition. If there is any unused capacity available prior to the activation, the
result is that the actual active count changes by more than the intended active count, and the
intended active count may not change at all. However, the discrepancy between intended active
and actual active is reduced. If there is no unused capacity available, the desired number of cores
will be activated in the virtual partition.
If you are adjusting core assignments across virtual partitions in a single nPartition, use the
vparmodify command for the best coordination between the iCAP software and the vPars
software, and for optimized performance. The vparmodify command is the fastest and most
Activations and deactivations in a virtual partition environment 45