IBM z/OS - page 38

LPAR CPU Management

LPAR CPU Management allows WLM working in goal

mode to manage the processor weighting and logical

processors across an LPAR cluster. CPU resources are

automatically moved toward LPARs with the greatest need

by adjusting the partition’s weight. WLM also manages

the available processors by adjusting the number of logi-

cal CPs in each LPAR. This helps optimize the processor

speed and multiprogramming level for each workload,

helps reduce MP overhead, and helps give z/OS more

control over how CP resources are distributed to help meet

your business goals.

z/OS 1.2 enhances the LPAR CPU management capa-

bilities and will allow the dynamic assignment of CPU

resources to non-z/OS partitions outside the z/OS LPAR

cluster such as Linux or z/VM.

Dynamic Channel Path Management

In the past, and on other architectures, I/O paths are

deﬁ ned with a ﬁ xed relationship between processors and

devices. With z/OS and the zSeries, paths may be dynami-

cally assigned to control units to reﬂ ect the I/O load. For

example, in an environment where an installation normally

requires four channels to several control units, but occa-

sionally needs as many as six, system programmers must

currently deﬁ ne all six channels to each control unit that

may require them. With Dynamic Channel Path Manage-

ment (DCM), the system programmer need only deﬁ ne the

four channels to the control units, and indicate that DCM

may add an additional two. As the control unit becomes

more heavily used, DCM may assign channels from a pool

of managed channels, identiﬁ ed by the system program-

mer, to the control unit. If the work shifts to other control

units, DCM will unassign them from lesser utilized control

units and assign them to what are now the more heavily

used ones. DCM is for ESCON and FICON Bridge chan-

nels and can help reduce the number of channels required

to effectively run a workload. DCM can also help reduce

the cost of the ﬁ ber infrastructure required for connectiv-

ity between multiple data centers. On a z990 with Logical

Channel SubSystems (LCSSs), the scope of DCM man-

agement is within a Logical Channel SubSystem. Although

an LPAR cluster can span LCSSs, when DCM is used it will

only consider systems in the same LPAR cluster and the

same LCSS.

Channel Subsystem Priority Queuing

The notion of I/O Priority Queuing is not new; it has been in

place in OS/390 for many years. With IRD, this capability

is extended into the I/O channel subsystem. Now, when

higher priority workloads are running in an LPAR cluster,

their I/Os will be given higher priority and will be sent to

the attached I/O devices (normally disk but also tape and

network devices) ahead of I/O for lower priority workloads.

LPAR priorities are managed by WLM in goal mode.

Channel Subsystem Priority Queuing provides two advan-

tages. First, customers who did not share I/O connectivity

via MIF (Multiple Image Facility) out of concern that a lower

priority I/O intensive workload might preempt the I/O of

higher priority workloads, can now share the channels and

reduce costs. Second, high priority workloads may even

beneﬁ t with improved performance if there were I/O con-

tention with lower priority workloads. Initially, Channel Sub-

system Priority Queuing is implemented for Parallel OEMI

and ESCON, FICON Bridge and native FICON channels.