Dynamic Chpid Management (Dcm) Considerations; I/O Priority Recommendations; Security-Related Controls; Logical Partition Isolation - IBM Z9 Planning Manual

Dynamic CHPID Management (DCM) Considerations

DCM CHPIDs used by WorkLoad Manager (WLM) to optimize I/O throughput
across an LPAR cluster are identified in the IOCDS by specifying CHPARM equals
01 and IOCLUSTER equals name (where name is an 8-byte EBCDIC cluster
identifier).
All DCM CHPIDs are inherently shareable by all LPs but reserved for use by the
WLM enabled members of the specified cluster. At completion of an LP activation,
its DCM CHPIDs will be in a deconfigured state. When an LP joins a cluster, the
DCM CHPIDs in that cluster become available for use by WLM but are not brought
online until the need for greater throughput arises. System reset of an LP that was
a member of a cluster causes each of the DCM CHPIDs that were online to the LP
to be deconfigured. For information on how to define DCM CHPIDs, see "IOCP
Statements for ICP" on page 2-28. For allocation rationale of DCM CHPIDs, see
redbook z/OS Intelligent Resource Director, SG24-5952.

I/O Priority Recommendations

Channel subsystem I/O priority queuing is used by z/OS WLM component to
dynamically manage the priority of I/O operations for given workloads based on the
performance goals for these workloads as specified in the WLM policy.
Channel subsystem I/O priority queueing is used by z/VM to manage the priority of
I/O operations performed by guests. The VM Resource Manager adjusts guest I/O
priorities based on the performance goals of the associated workloads. It is
recommended that you establish a range of I/O priorities for z/VM logical partitions
that is sufficient to enable effective discrimination among guest I/O requests of
different importance.
In order to provide WLM the greatest flexibility in managing I/O requests across
members of an LPAR cluster, it is highly recommended that you establish the same
range of priorities for each member of an LPAR cluster. A range of eight priorities
(from minimum to maximum) is optimum. If a range greater than eight is specified,
only the top eight will be utilized by WLM.
Non-WLM managed LPs should be assigned I/O priorities according to their
importance relative to the LPs that are members of LPAR clusters. Unless it is
running z/VM (in which case the recommendations above should be followed), a
non-WLM managed LP should be assigned equal values for minimum and
maximum I/O priorities. For more information and examples of how I/O priorities are
used by WLM to prioritize I/O requests across diverse workloads, see redbook z/OS
Intelligent Resource Director, SG24-5952.

Security-Related Controls

You can define security-related controls for an LP.

Logical Partition Isolation

This control reserves reconfigurable unshared channel paths for the exclusive use
of an LP. Channel paths assigned to an isolated LP are not available to other LPs
and remain reserved for that LP when they are configured offline.
Use the Release task available from the CHPID Operations task list to release an
unshared channel path from an isolated LP.
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PR/SM Planning Guide