HP Instant Capacity Version 10.x User Guide (5900-1581, March 2011)
Whenever you have more active cores than the number of core usage rights, the temporary capacity
balance is depleted as a mechanism for tracking noncompliance of the group, even if TiCAP has
not been purchased for or applied to any member of the group. This differs from the behavior of
TiCAP on a complex which is not a member of a group, where TiCAP is decremented only if TiCAP
had been specifically purchased for the complex. Within a GiCAP group, temporary capacity is
used as an additional compliance mechanism to support the high availability features of a group.
Because group members are automatically considered to be users of temporary capacity, to avoid
unexpected TiCAP depletion in a group, it is important to avoid the situations that cause the Instant
Capacity software to make assumptions that all cores might be active on a remote nPartition.
If a member is removed from the group, the TiCAP balance on that complex will continue to be
used as a compliance mechanism (decremented whenever the number of active cores exceeds the
number of core usage rights), unless the TiCAP balance on the system is exactly 0.
Status Reporting
Usage rights and temporary capacity can sometimes be temporarily assigned to the Group Manager,
which can result in difficulty interpreting some of the data from the icapstatus command. The
total temporary capacity reported for the group by icapmanage -s might not equal the sum of
temporary capacity reported by each member system. This is because the Group Manager prefetches
an amount of temporary capacity in anticipation of needing it for a future operation, so the
temporary capacity might not be immediately assigned to a member system. Also, individual counts
of cores, cells, and memory without usage rights for each member of the group might not add up
to the total counts of cores, cells, and memory without usage rights for the group. In all cases, totals
reported (by icapmanage -s) for group temporary capacity and usage rights are the important
values that represent available resources for the group. Use the verbose (-v) option to the
icapmanage -s command to see resources held by the Group Manager.
The icapstatus command reports usage rights borrowed or loaned by the system from or to
other members of the group. Borrowed rights are those that are currently resident on the member
and that originated elsewhere. Loaned rights originate on the system but are currently resident
somewhere else in the group. They might be either in use or unassigned on another group member,
or they might be unassigned on the Group Manager itself. The icapmanage -s command displays
the status of the entire group, while the icapstatus command displays an isolated view of a
single member.
Unassigned usage rights are free to be moved to other member systems, even if a particular
activation request fails. For example, consider a group where there are no free usage rights. If
member m1 releases 2 core usage rights by deactivating 2 cores, and member m2 tries to activate
3 cores, the activation request fails (not enough usage rights), after the Group Manager has already
migrated 2 core usage rights from m1 to m2. The borrow and loan values for m1 and m2 show that
the loan has occurred, even though the activation on m2 failed to activate any cores. A subsequent
activation of 2 cores on m2 will be successful and will occur more quickly because the 2 core
usage rights are already assigned to m2, or because the rights are moved elsewhere in the group
if requested.
Example: Cell/Memory Sharing
In this scenario, member1 of the group mygroup has an inactive cell it wants to activate, but no
usage rights are available on the system. However, member2 of the group has available usage
rights.
First, the output from the icapstatus command on member1 shows that no cell or memory usage
rights are available:
Instant Capacity Resource Summary
---------------------------------
Number of cells without usage rights: 1
Number of inactive cells: 1
Amount of memory without usage rights: 16.0 GB
Global Instant Capacity Resource Sharing 79