CICSplex, CICSPlex SM, and Parallel Sysplex

There is considerable synergy between CICSplex, CICSPlex® SM, and Parallel Sysplex®, and used in combination, they can provide the highest possible availability and continuous operations for CICS® applications.


Multiple CICS regions can communicate with each other and cooperate to handle inbound work requests. This specialized type of cluster is referred to as a CICSplex. In the CICS environment, CICSplex provides many benefits, including superior scalability, single system image, and so on. A CICSplex is managed as a single entity. It is a significant technology for high availability and continuous operation for CICS workloads. However on its own, it can do nothing about the availability of other subsystems or data, which might be required to fulfill the CICS application business needs (for example, access to DB2® data).


The CICSPlex SM element of CICS TS is the system management infrastructure that has the capability to manage multiple CICS systems (a CICSplex) across multiple images from a single control point. Enterprises in which CICSPlex SM might be needed range from those running only a few CICS systems to those running hundreds of CICS regions or more. In the many large z/OS® sysplex environments, a large number of CICS systems can be needed to support the transaction processing workload. Workload management, real-time analysis, and monitoring services are used to manage the CICSPlex SM configuration and CICSplex environment, and to gather statistical information.

CICSPlex SM provides a real-time, single-system image of all CICS regions and resources that make up each CICSplex in the transaction processing environment. It provides a single point of control for the definition and deployment of resources in a CICSplex.

The CICSPlex SM workload manager dynamically routes transactions and provides workload management for all dynamic transactions and program links across CICS systems in the target scope, taking into account region availability, and honoring any workload affinity and workload separation requirements.

Parallel Sysplex

When you have a single copy of any system component, hardware, software, or data, you are inevitably exposed to system outages because of either failure of the component or because of planned changes to the component that require it to be taken offline.

One of the goals of Parallel Sysplex is to eliminate the impact that scheduled outages have on application availability, and minimize the effects of an unscheduled outage by allowing work to continue executing on the remaining systems in the sysplex. This requires, among other things, that the system is designed for redundancy within the Parallel Sysplex. Applications must be able to run across multiple systems, with access to the data possible from at least two systems. If at least two instances of a resource exist, your applications can continue to run even if one of the resources fails.
Note: Parallel Sysplex provides only the facilities for continuous availability. Parallel Sysplex on its own does not eliminate scheduled or unscheduled application outages; the application itself must also be designed for continuous availability. Sharing data is only one part of this design.
Parallel Sysplex provides the facilities that can be exploited by subsystems and applications that are running in the sysplex to provide higher availability, simplified systems management, and improved scalability. For example:
  • XCF services allow authorized programs on one system to communicate with programs on the same system or on other systems. If a system fails, XCF services also provide the capability for batch jobs and started tasks to be restarted on another eligible system in the sysplex.
  • The coupling facility enables parallel processing and improved data sharing for authorized programs that are running in the sysplex.
In the CICS environment, for example:
  • CICS can directly exploit Parallel Sysplex by sharing nonrecoverable temporary storage queues via a coupling facility.
  • CICS can indirectly exploit Parallel Sysplex by utilizing VSAM RLS sysplex-wide record-level locking (in this example, DFSMS VSAM could be considered the direct exploiter).
  • CICSPlex SM sysplex optimized workload management can directly exploit Parallel Sysplex by obtaining region status information from a coupling facility.

CICSplex, CICSPlex SM, and Parallel Sysplex in combination

In the CICS environment, CICSplex and CICSPlex SM provide a single-system image, workload management, and to some extent a data sharing capability, but just for CICS. A Parallel Sysplex provides a single-system image and a data sharing capability for all appropriately configured workloads, not just CICS. With the proper Parallel Sysplex design and configuration, this can prevent an outage against a CICS application, just because, for example, a subsystem, or even an entire z/OS system, has become unavailable.