Recovery Considerations; Determining The Characteristics; Control Program Support; Capped Logical Partitions - IBM Z9 Planning Manual

Capped Logical Partitions

It is recommended that LPs be defined as capped LPs at the Support
Element/Hardware Management Console only when needed to support planned
requirements. When a capped LP does not obtain needed CP resources, because it
has reached its cap, activity for that LP is similar to a system running out of CP
resources. Response time can be slower on systems which operate at their cap.
For this reason, interactive response times can suffer when there is a mix of
interactive and CP-intensive work in the same capped LP.

Recovery Considerations

Resources should be defined to LPs so that any hardware failure has a minimal
impact on the remaining active LPs.
For example, the failure of a physical CP can cause the temporary loss of any
logical CP that was dispatched on the physical CP. In many instances, recovery of a
logical CP that was running on a failed physical CP will take place automatically
when an available spare physical CP is dynamically brought into the configuration.
Also, PR/SM LPAR is often able to transparently re-dispatch a shared logical CP on
a different physical CP even when no spares are available. If a logical CP is still
lost, the LP owning the logical CP can continue operating if it was running on an LP
with at least two CPs dispatched on different physical CPs, and if the control
program that is active in the LP can recover from CP failures.

Determining the Characteristics

The information in this section should help you determine the type and amount of
CPC resources you need for each LP.
The total amount of resources that you can define for all LPs can exceed the
configured resources.
Individual LP definitions are checked against the total resources installed. The
actual allocation of these resources takes place only when the LP is activated. This
design characteristic allows considerable flexibility when defining and activating
LPs.

Control Program Support

Table 3-1 on page 3-6 summarizes the characteristics of the control programs that
can be supported in an LP. See "Control Program Support in a Logical Partition" on
page 1-5 for more information.
Some control programs require specific LP characteristics. For this reason consider
all control programs before planning or defining LP characteristics.
Chapter 3. Determining the Characteristics of Logical Partitions
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