Chapter 7. Sysplex functions 177
Draft Document for Review April 7, 2004 6:15 pm 6947ch07.fm
IRD addresses three separate but mutually supportive functions:
򐂰LPAR CPU management
WLM dynamically adjusts the number of logical processors within a logical partition and
the processor weight based on the WLM policy. The ability to move the CPU weights
across an LPAR cluster provides processing power to where it is most needed based on
WLM goal mode policy.
򐂰Dynamic channel path management (DCM)
DCM moves channel bandwidth between disk control units to address current processing
needs. The z990 supports DCM within a Logical Channel Subsystem.
򐂰Channel Subsystem Priority Queuing
This feature on the zSeries allows the priority queueing of I/O requests in the Channel
Subsystem and the specification of relative priority among logical partitions. WLM in goal
mode sets the priority for a logical partition and coordinates this activity among clustered
logical partitions.
7.5.1 LPAR CPU management
LPAR CPU management allows WLM working in goal mode to manage the processor
weighting and logical processors across an LPAR cluster.
LPAR CPU management was enhanced in z/OS 1.2 to dynamically manages non-z/OS
operating systems such as Linux and z/VM. This function allows z/OS WLM to manage the
CPU resources given to these partitions based on their relative importance compared to the
other workloads running in the same LPAR cluster.
Workload Manager distributes processor resources across an LPAR cluster by dynamically
adjusting the LPAR weights in response to changes in the workload requirements. When
important work is not meeting its goals, WLM will raise the weight of the partition where that
work is running, thereby giving it more processing power. As the LPAR weights change, the
number of online logical CPUs may also be changed to maintain the closest match between
logical CPU speed and physical CPU speed.
LPAR CPU management runs on a zSeries server in z/Architecture mode, and in LPAR mode
only. The participating z/OS system images must be running in goal mode. It also requires a
CF level 9 or above Coupling Facility structure.
Enabling LPAR CPU management involves defining the Coupling Facility structure and then
performing several operations on the hardware management console: defining logical CPs,
and setting initial, minimum, and maximum processing weights for each logical partition.
CPU resources are automatically moved toward logical partitions with the most need by
adjusting the partition’s weight. The sum of the weights for the participants in an LPAR cluster
is viewed as a pooled resource that can be apportioned among the participants to meet the
goal mode policies. The installation can place limits on the processor weight value.
WLM will also manage the available processors by varying off unneeded CPs (more logical
CPs implies more parallelism, and less weight per CP).
Note: In order to manage non-z/OS images, such as Linux, z/VM, VM/ESA, TPF, z/VSE or
VSE/ESA, at least one image in the LPAR Cluster must be running z/OS 1.2 or higher.