IBM Z9, Planning Manual

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Application Preservation
The application preservation facility enhances system availability and provides
additional protection from CP failures. This support is available on System z9 CPC
models with two or more central processors (CPs). Using application preservation,
the system moves an application in process from a failing CP to another operating
CP. Both the CP failure and the move are transparent to the application.
There are no software corequisites when running with shared CPs. For LPs using
shared CPs, even 1-way LPs can survive a CP failure without experiencing a failure
to the application or the LP, providing the 1-way LP is being run on a model with
more than one physical CP.
Transparent Sparing
Transparent sparing takes LP recovery one step further by combining the benefits
of application preservation and concurrent CP sparing to allow for the transparent
recovery of an LP and its applications (including CF LPs). Transparent sparing uses
hardware to handle the recovery, requires no software support or operator
intervention, and is effective for both shared and dedicated LP environments.
Transparent sparing configures a spare PU (processor unit) to replace a failed CP,
ICF, IFL, IFA, zIIP or SAP. Each z9 EC has 2 spare PUs per processor book. The
S08 has 2 spare PUs, the S18 has 4, the S28 has 6, the S38 has 8, and the S54
has 8.
Chapter 5. Monitoring the Activities of Logical Partitions
5-11