IBM 990 - Manual (Page 181)

Chapter 7. Sysplex functions 169
Dynamic ICF expansion can also be configured using dedicated ICF PUs and shared CPs
from the z/OS image. The z/OS image
must have all CPs defined as shared and the Dynamic
CF Dispatch function must be activated. Dynamic ICF Expansion is available on z990 models
that have at least one ICF.
Dynamic ICF Expansion requires that Dynamic CF Dispatching be activated (DYNDISP ON).
Figure 7-6 z990 CF options - Dynamic ICF Expansion
7.3 System-managed CF structure duplexing
System-managed Coupling Facility structure duplexing provides a general purpose,
hardware-assisted, easy-to-exploit mechanism for duplexing CF structure data. This provides
a robust recovery mechanism for failures, such as loss of a single structure or Coupling
Facility, or loss of connectivity to a single Coupling Facility, through rapid failover to the other
structure instance of the duplex pair.
7.3.1 Benefits
Benefits of system-managed CF structure duplexing include:
Availability
Faster recovery of structures is provided by having the data already in the second
Coupling Facility when a failure occurs. Furthermore, if a potential IBM, vendor, or
customer Coupling Facility exploitation were being prevented, due to the effort required,
from providing alternative recovery mechanisms such as structure rebuild, log recovery,
and so forth, system-managed duplexing could provide the necessary recovery solution.
Manageability and usability
These benefits are achieved by a consistent procedure to set up and manage structure
recovery across multiple exploiters.
z/OS
Prod
z/OS
Prod
Function
Setup
HMC
z990
Partition
Image
Profile
ICF CP
CF CF
Test Sysplex
z/OS
Test z/OS
Test CF
DYNDISP ON (CFCC cmd)
IMAGE Profile setup
Shared Pool of ICF PUs
Dedicated ICFs used for most of the CF requests
Shared ICFs used when requests rates to CF become excessive
Shared ICFs used for take over or spikes (such as alternate CF
removed for maintenance or outage occurs)