2. PERFORMANCE REPORTING ANALYSIS › 2.6 PR/SM LPAR Performance Analysis › 2.6.2 PR/SM LPAR Concepts

2.6.2 PR/SM LPAR Concepts

The PR/SM feature is a hardware facility that was made
available by IBM starting with the IBM 3090E and 3090S series
processors.  It is an intermediate step between physical (or
hardware) partitioning, such as the reconfiguration of a
3090-400E into the equivalent of two separately IPLable
3090-200E systems, and software partitioning, as implemented
in the Virtual Machine Facility (VM).

PR/SM allows multiple operating System Control Programs
(SCPs), such as MVS/XA or MVS/ESA, to share the facilities of
a single Central Electronic Complex (CEC) or one side of a
physically partitioned complex.  A CEC or physical partition
can be initialized either in logical partition (LPAR) mode or
in basic mode.  In basic mode, the functions of PR/SM are not
available.

PR/SM hardware is utilized by two IBM products:  a microcode
feature called Logical Partitioning Mode and VM/XA Multiple
Preferred Guest.  The hardware feature can support either of
these two products, but not both simultaneously.  The
discussion which follows addresses only logical partitioning
mode operations.

The processor, storage, and I/O resources of the processor
complex can be divided and allocated to several logical
partitions (LPARs), which can then be IPLed and operated
independently of each other.  Up to ten LPARs per physical
partition are allowed, meaning that a CEC that supports
physical partitioning can have up to ten per side for a
maximum of twenty LPARs, while a non-partitionable complex is
limited to ten.  Throughout this chapter, the terms CEC and
complex are used interchangeably, and can be taken to refer
to one half of a physically partitioned complex.

The following sections discuss PR/SM operations and controls
allowing an analyst to optimally configure and operate a CEC:

    1 - Overview of PR/SM LPAR Operation
    2 - Controlling the PR/SM LPAR Environment