LPAR CPU management

When you divide your central processing complex into separate logical partitions, each partition is assigned its own LPAR weight, which corresponds to the percentage of overall processing power that is guaranteed to the work in that partition. Previously, if the workload shifted to the extent that more processing power was needed in a particular partition, the weights had to be changed manually. With LPAR weight management, you give each logical partition an initial LPAR weight, along with an optional minimum and maximum weight if desired. WLM will then dynamically balance these weights to best meet the goals of the work in the partitions, with no human intervention. Note that the total weight of the cluster as a whole will remain constant, so LPARs outside the cluster are unaffected.

LPAR weight management takes effect when two or more LPARs in the cluster are running CPU-constrained, and the CPC’s shared physical CPs are fully utilized. When just one LPAR is using all or most of the CPC because other LPARs are idle, then LPAR weight management will have no effect on resource distribution.

If there are non z/OS® partitions in the LPAR cluster, the Intelligent Resource Director manages the weight of these partitions by exchanging weight between the non z/OS and the z/OS partitions of the cluster. LPAR weight of any non z/OS partition will not be reset to its initial weight when the z/OS partition is reset or deactivated. Non z/OS partitions weight can be reset through the service element panel in this situation.

VARY CPU Management works for z/OS partitions only. It works hand-in-hand with LPAR weight management. As the LPAR weights change, the number of online logical CPUs is also changed to maintain the best match between logical CPU speed and physical CPU speed. Optimizing the number of logical CPUs benefits workloads that have large amounts of work done under single tasks, and minimizes LPAR overhead for all workloads.