What is a Sysplex?

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  • Written By: N.M. Shanley
  • Edited By: Michelle Arevalo
  • Last Modified Date: 11 October 2019
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A group of IBM computers or systems communicating with each other creates a system complex, or Sysplex. This connection allows computer processors to share the system's workload. Using this technology increases speed and efficiency, as system users can rely on several machines and processors, instead of one core processor.

This shared functionality is facilitated by IBM's Cross-system Communications Facility (XCF). XCF is the software that manages the connections between computers. XCF ensures constant communication between all computers on the system. As a result, information is updated across the system virtually instantaneously.

Disaster recovery is an important use for this IBM technology. Sysplex adds a Sysplex Timer® to all connected systems. This ensures that all systems share the exact same time stamp. Identical time stamps make it possible to recover and restore information from various systems. Without this time stamp, different systems would not be in sync and may not be able to restore the same information.

IBM launched Sysplex in 1991 for mainframes running its MVS/ESA operating system. The next generation of this technology for use with IBM's 390 operating system, called Parallel Sysplex®, was launched in 1994. A major development in the parallel version was to allow all connected systems to work together as a single system.


This parallel technology enables users to access the same information simultaneously from different computers. Requested changes to shared information are made in order, or serialized, to prevent any changes from being lost. For example, bank teller computers can be part of a Parallel Sysplex®. When a banking transaction is completed, the same updated account information will be displayed on all bank terminals, even if they are located in different branches.

Time stamping has also been updated in the last parallel technology. In earlier versions, the Sysplex Timer® was an additional piece of hardware separate from the mainframe. In 2005, the timer hardware was replaced by Server Time Protocol (STP) for System z mainframe models z980 and newer. STP is embedded in the mainframe's code, eliminating the need for additional hardware.

IMB's Workload Manager (WLM) was also introduced with Parallel Sysplex® to increase resource sharing efficiency. WLM sends requests to parts of the system with the lightest workload at a specific time. Using WLM, the user can define goals and set priorities within the system. WLM will then assign available resources to each system request according to this user-defined information. WLM constantly monitors the system resources and adapts data processing to met the goals set up by the user.


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