IBM eServer zSeries 990 Technical Guide

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

Te st S yspl e x

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)