6. DATA SOURCES › 6.8 PR/SM LPAR Concepts › 6.8.1 Introduction

6.8.1 Introduction

The PR/SM feature is an intermediate step between physical
(or hardware) partitioning, such as the reconfiguration of a
4-processor system into the equivalent of two separately
IPLable 2-processor systems, and software partitioning, as
implemented in the Virtual Machine Facility (VM).

PR/SM allows multiple Operating System Control Programs
(SCPs), such as z/OS or z/VM, to share the facilities of a
single central processor complex (CPC) or one side of a
physically partitioned complex.  The PR/SM hardware can be
used by two IBM products:  a microcode feature called Logical
Partitioning Mode (LPAR) and Virtual Machine Facility
Multiple Preferred Guest.  The PR/SM hardware can support
either of these two products, but not both simultaneously.
This is because the CPC or physical partition must be
reinitialized to switch from one mode to the other.

This chapter addresses only LPAR mode operations.

The processor, storage, and I/O resources of a PR/SM-equipped
processor complex can be divided and allocated to several
logical partitions, which can then be IPLed and operated
independently of each other.  Up to sixty partitions per
physical partition are allowed.  Further on in this chapter,
the terms CPC and complex are used interchangeably, and refer
to one half of a physically partitioned complex as well as
the entire complex.

SCPs that are supported for operations in a complex
initialized in LPAR mode are:

o  z/OS        o  z/TPF
o  z/VM        o  Linux on System z
o  z/VSE