 - A sysplex is IBM's systems complex (the word sysplex comes from the
first part of the word system and the last part of the word
complex), introduced in 1990 as a platform for the MVS/ESA
operating system for IBM mainframe
servers. An enhanced version, Parallel Sysplex, was
subsequently introduced for the newer operating system, OS/390. The
sysplex consists of the multiple computers (the systems) that make up the
complex. A sysplex is designed to be a solution for business needs involving any
or all of the following: parallel processing; online transaction
processing (OLTP); very high transaction volumes; very numerous
small work units - online transactions, for example (or large work units that
can be broken up into multiple small work units); or applications running
simultaneously on separate systems that must be able to update to a single
database without compromising data integrity.
According to IBM, the Parallel Sysplex is the end result of IBM large
systems' developments over the years, from the single system uniprocessor, to
tightly-coupled multiprocessors, to loosely-coupled
configurations, to the sysplex, and finally to the Parallel
Sysplex. A single system uniprocessor consists of a single central processor
complex (CPC) - which consists of a single central processor (CP)
and all associated system hardware and software, controlled by a single copy of
the operating system. Tightly coupled multiprocessors consist of a number of CPs
added to a CPC that share central storage and a single copy of the operating
system. Work is assigned to an available CP by the operating system and can be
rerouted to another if the first CP fails. A loosely coupled configuration has
multiple CPCs (which may be tightly coupled multiprocessors) with separate
storage areas, managed by more than one copy of the operating system and
connected by channel-to-channel communications.
A sysplex is similar to a loosely coupled configuration, but differs in that
it has a standard communication mechanism (the cross-system coupling facility,
or XCF) for MVS system applications that enables communication between
application programs on one or multiple computers. The sysplex is made up of a
number of CPCs that collaborate, through specialized hardware and software, to
process a work load. This is what a large computer system does in general; a
sysplex, through XCF, increases the number of processing units and operating
systems that can be connected.
The Parallel Sysplex, IBM's latest method of configuration for CPCs, is a
clustering architecture that has improved communication
capabilities and supports more connected CPCs and more copies of the operating
system. There are several areas of improvement over the base sysplex. The
Parallel Sysplex Coupling Facility is a new processor that stores crucial system
information, usually configured on a separate device. Use of the coupling
facility increases the capacity for data sharing among systems and subsystems.
Because it is used through both systems and subsystems, it also ensures data
integrity and consistency throughout the sysplex. Another feature of the new
technology is the Workload Manager (WLM), part of OS/390 that is in each system
in a Parallel Sysplex configuration. WLM manages resources more responsively
than the earlier schedule-based methods through dynamic workload
balancing and prioritization according to user-set criteria. The data-sharing
capability enables simultaneous, multiple-system access to data.
| LAST UPDATED: |
27 Mar 2007
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