6947ch02.fm Draft Document for Review April 7, 2004 6:15 pm
48 IBM eServer zSeries 990 Technical Guide
Within the limit of all non-characterized PUs available in the installed configuration, IFLs can
be concurrently added to an existing configuration via Capacity Upgrade on Demand (CUoD),
Customer Initiated Upgrade (CIU), On/Off Capacity on Demand (On/Off CoD), but IFLs
cannot be assigned via CBU. For more information about CUoD, CIU or On/Off CoD see
Chapter 8, “Capacity upgrades” on page185. If the installed books have no unassigned PUs
left, the assignment of the next IFL may require the installation of an additional book.
Internal Coupling Facilities
An Internal Coupling Facility (ICF) is a PU used to run the IBM Coupling Facility Control Code
(CFCC) for Parallel Sysplex environments. Within the capacity of the sum of all unassigned
PUs in up to four books, up to 16 ICFs can be characterized, depending on the z990 model.
You need at least an IBM 2084 model B16 to assign 16 ICFs. ICFs can be concurrently
assigned to an existing configuration via Capacity Upgrade on Demand (CUoD), On/Off
Capacity on Demand (On/Off CoD), or Customer Initiated Upgrade (CIU), but ICFs cannot be
assigned via CBU.
For more information about CUoD, CIU, or On/Off CoD see Chapter8, “Capacity upgrades”
on page 185. If the installed books have no non-characterized PUs left, the assignment of the
next ICF may require the installation of an additional book.
The ICF processors can only be used by Coupling Facility logical partitions. ICF processors
can be dedicated to a CF logical partition, or shared by multiple CF logical partitions running
in the same z990 server.
All ICF processors within a configuration are grouped into the ICF/IFL/zAAP processor pool.
The ICF/IFL/zAAP processor pool appears on the hardware console as ICF processors. The
number of ICFs shown is the sum of IFL, ICF, and zAAP processors on the system.
Only Coupling Facility Control Code (CFCC) can run on ICF processors; ICFs do not change
the model type of the z990 server. This is important because software product license
charges based on the software model number are not affected by the addition of ICFs.

Dynamic ICF Expansion

Dynamic ICF Expansion is a function that allows a CF logical partition running on dedicated
ICFs to acquire additional capacity from the LPAR pool of shared CPs or shared ICFs. The
trade-off between using ICF features or CPs in the LPAR shared pool is the exemption from
software license fees for ICFs. Dynamic ICF Expansion is available on any z990 model that
has at least one ICF.
Dynamic ICF Expansion requires that the Dynamic CF Dispatching be turned on (DYNDISP
ON). For more information, see “Dynamic CF dispatching and dynamic ICF expansion” on
page 166.

Dynamic Coupling Facility Dispatching

The Dynamic Coupling Facility Dispatching function has an enhanced dispatching algorithm
that lets you define a backup Coupling Facility in a logical partition on your system. While this
logical partition is in backup mode, it uses very little processor resource. When the backup CF
becomes active, only the resource necessary to provide coupling is allocated.
The CFCC command DYNDISP controls the Dynamic CF Dispatching (use DYNDISP ON to
enable the function). For more information, see “Dynamic CF dispatching and dynamic ICF
expansion” on page166.