IBM Z9, Planning Manual

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Coupling Facility
Configuration
All
Dedicated
CPs or
ICF(s)
Dedicated
ICF(s) and
Shared
CP(s)
Dedicated
ICF(s) and
Shared
ICF(s) Shared ICF Shared CP Shared ICF
CF Model — — —
System z9
with only ICF
processors
System z9
with 1 or
more general
purpose CPs
System z9
with 1 or
more general
purpose CPs
Dynamic Dispatching
Default Value Off On On Off On Off
Dynamic Dispatching
Forced? No Yes Yes No No No
System-Managed Coupling Facility Structure Duplexing
A set of parallel sysplex architectural extensions is provided for support of
system-managed duplexing of coupling facility structures for high availability. All
three structure types, cache, list, and locking, can be duplexed using this
architecture.
Benefits of system-managed CF structure duplexing include:
v Availability: Faster recovery of structures by having the data already in the
second CF.
v
Manageability and Usability: A consistent procedure to set up and manage
structure recovery across multiple exploiters
v Cost Benefits: Enables the use of non-standalone CFs (for example, ICFs) for
all resource sharing and data sharing environments.
Preparations for CF duplexing include the requirement to connect coupling facilities
to one another with coupling links. The required CF-to-CF connectivity is
bi-directional, so that signals may be exchanged between the CFs in both
directions. A single peer-mode coupling link between each pair of CFs can provide
the required CF-to-CF connectivity; however, for high availability at least two
peer-mode links between each pair of CFs are recommended.
Note that while peer-mode CHPIDs cannot be shared between multiple coupling
facility images, they can be shared between a single coupling facility image and one
or more z/OS images. With this sharing capability, a single peer-mode ISC-3 or ICB
link can serve both as a z/OS-to-CF link and as a CF-to-CF link, and thus provide
the connectivity between z/OS and CF partitions as well as the connectivity
between CFs that is required for CF Duplexing. Of course, at least two such links
are recommended for high availability. In addition IFB links can provide the ability to
actually share the same physical link between multiple CF images. By defining
multiple CHPIDs on the same physical IFB link, the individual CHPIDs can be
defined for a single CF image while the physical link is being shared by multiple CF
images.
Single CPC Software Availability Sysplex
For single CPC configurations, System z9 models can utilize an ICF to form a
single CPC sysplex, providing significant improvement in software continuous
operations characteristics when running two z/OS LPs in data-sharing mode versus
one large z/OS image. For these configurations, overall RAS is improved over that
provided by a single z/OS image solution. Hardware failures can take down the
entire single CPC sysplex, but those failures are far less frequent than conditions
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PR/SM Planning Guide
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