6. DATA SOURCES › 6.8 PR/SM LPAR Concepts › 6.8.2 How PR/SM Works › 6.8.2.1 Introduction to LPAR CPU Management › 6.8.2.1.1 WLM LPAR Weight Management

6.8.2.1.1 WLM LPAR Weight Management

In an LPAR environment, access to central processors is based
on the active partitions' relative weights.  When an LPAR is
not managed by WLM, its processing weight is set when the
partition is defined and can be modified at any time by the
console operator.  The problem is, that, if the workload mix
changes, weights would have to be manually adjusted in order
to optimize the CPU resource utilization.  This would require
24/7 human monitoring of the workload performance, as well as
an outstanding ability to anticipate workload variations, not
an easy task in the new eBusiness world.  Alternatively, you
could configure enough capacity to handle peak periods, but,
outside of these periods, the excess capacity goes unused,
and, therefore, is lost.

With WLM LPAR weight management, the relative shares of the
participating partitions will be automatically adjusted, so
that the LPARs hosting the most important workloads, based on
WLM policy, get the necessary CPU resources.

This process occurs within a set of partitions, explicitly
defined as being managed by WLM, an LPAR cluster, and the
total weight of the cluster remains constant.  This way,
LPARs outside of the cluster, are not affected.