CICS fundamentals

This section introduces you to the components and concepts of CICS®.

CICS topology
You can distribute CICS applications and the resources they use between interconnected CICS regions. You can group CICS regions into CICS system groups and CICSplexes, and distribute regions across the z/OS® systems in a sysplex.
CICS resources
Before you can run a program in CICS, you must supply CICS with information about system resources, including software resources such as programs and data, and hardware resources such as terminals or communications links. At a minimum, you must define a transaction.
What is a CICS application?
An application is a collection of related programs that together perform a business operation, such as processing a product order, or preparing a company payroll. CICS applications execute under CICS control, using CICS services and interfaces to access programs and files.
CICS and Java
CICS provides the tools and runtime environment to develop and run Java™ applications in a Java Virtual Machine (JVM) that is under the control of a CICS region.
CICS and Node.js
Node.js is a server-side run time for applications that are written in JavaScript.
Making asynchronous requests
Using the asynchronous API commands provided with CICS is a simple way to issue requests to external services and have them run asynchronously. Instead of calling each service sequentially and waiting for a response, the asynchronous API commands provide a simple and powerful way to write asynchronous applications which save wait time and frees up your program to continue with other processing.
Event processing overview
An event is anything that happens that is significant to an enterprise. Event processing is the capture, enrichment, formatting and emission of events, the subsequent routing and any further processing of emitted events (sometimes in combination with other events), and the consumption of the processed events.
FEPI concepts and facilities
The Front End Programming Interface (FEPI) is an integral part of CICS. You can use the interface to write CICS applications that simulate terminals to access other CICS or IMS programs. This type of application is called a front end application.
Cloud-enabling CICS Transaction Server for z/OS
Cloud is a conceptual shift in how businesses offer services. It drives increased operational efficiency over the management and operation of services and increases agility in developing and deploying them. CICS Transaction Server for z/OS provides three key capabilities as building blocks to transform existing CICS TS topologies and applications into cloud-style platforms and services. These are: platforms, applications as single entities, and policies to control operations. CICS bundles also play a part as a way of grouping and managing related resources for use by applications or platforms.
CICS policies
The behavior of CICS can be controlled during run time, based on predefined policies. CICS performs the action that is defined for a policy rule when all the conditions specified by the rule are met.
CICS intercommunication
CICS is often used as a single system with associated data resources and a network of terminals. However, CICS can also be used in a multiple-system environment, in which it can communicate with other systems that have similar communication facilities. This sort of communication is called CICS intercommunication.
CICS web support
CICS web support is a collection of CICS services that enable a CICS region to act both as an HTTP server, and as an HTTP client.
CICS and web services
CICS provides support for web services.
CICS external interfaces
CICS provides a number of interfaces that make transaction processing services available to a variety of external users.
Access to databases and data sets
CICS supports access to external data in Db2® and DL/I databases and in VSAM and BDAM data sets.
Workload management
Workload management generally means effectively distributing work around a system so that it can run in the most efficient way. In the context of CICS workload, it is the process of routing work to CICS regions so that the work can be efficiently executed. Workload management can occur before the work reaches CICS: for example, by selecting a CICS terminal-owning region (TOR) as the start point for a transaction. Or it can occur after the work arrives in CICS: for example, by selecting an appropriate region in CICS (typically, an application-owning region, or AOR) to which the transaction is routed. With CICS, there are a number of options for workload management.
CICSPlex SM overview
The CICSPlex® System Manager element of CICS Transaction Server for z/OS is a system management tool that enables you to manage multiple CICS systems from a single control point.
CICS management client interface (CMCI)
The CICS management client interface (CMCI) is a system management application programming interface (API) for use by HTTP client applications such as IBM® CICS Explorer®. The CMCI provides the CMCI REST API and the CMCI GraphQL API for clients to manage installed and definitional system resources, and the CICS bundle deployment API to deploy bundles into single CICS development regions with Maven and Gradle plug-ins. It also supports advanced client authentication, including multifactor authentication (MFA).
CICS and Business Transaction Services (BTS)
Read this introductory information to learn about CICS business transaction services (BTS).
CICS and IBM MQ
CICS provides a number of ways to run work in CICS using IBM MQ messages. From Java applications, you can access IBM MQ through IBM MQ classes for Java or IBM MQ classes for JMS. From other applications, you can access IBM MQ through two interfaces that are supplied with CICS: the CICS-MQ adapter and the CICS-MQ bridge.
CICS feature toggles and continuous delivery
In order to meet growing needs for more rapid delivery of key capabilities, CICS TS continuous delivery makes new functional enhancements available on a much shorter cadence so that you can use them without waiting for the next release. Some of these new capabilities require changes to the CICS configuration - the kind of changes that you would previously expect only with a new release of CICS TS. To make it easier for you to make the necessary configuration changes between releases to enable the new capabilities, feature toggles are introduced, giving you great flexibility and control in enablement and disablement of such capabilities during run time.
Provisioning CICS with z/OS Provisioning Toolkit
With the IBM z/OS Provisioning Toolkit, application developers can independently, and rapidly, provision and deprovision a development environment without needing mainframe administration skills or authorities. System programmers can automate the provisioning process while retaining control by using IBM z/OS Management Facility (z/OSMF) workflows. Sample images for provisioning commonly used CICS environments such as CICS TS with an embedded Liberty JVM server, or standard CICS TS for traditional COBOL development, are provided with the z/OS Provisioning Toolkit.
Monitoring your CICS workload
Monitoring is the process of collecting and reporting data about the items of work in a system. Monitoring data provides information which workload managers can use to make their decisions. You can analyze monitoring data reports to choose or adjust performance goals for the system, tackle any performance problems through tuning activities, and make decisions about your future strategy and investments. There are a number of CICS and z/OS components, and some separate tools, which you can use for workload monitoring of your CICS regions.
Threadsafe learning path
This learning path provides an overview of open transaction environment (OTE) threadsafe options. Using the OTE you can obtain throughput improvements on multiprocessors, providing that the application code is threadsafe. The options available to get different types of threadsafe applications to use the OTE are explained and a summary is provided with links to further reading.
Sysplex optimized workload management learning path
Sysplex optimized workload management takes advantage of the z/OS Coupling Facility (CF) to store current region status information posted directly from CICS. The stored region status is then used to make more efficient routing decisions. In this learning path, you learn about optimizing your workloads by implementing a region status (RS) server, the benefits you can expect, how to determine your optimization status, storage utilization, impact on the coupling facility, and RS server tuning parameters.
Accessibility of CICS Transaction Server
Accessibility features help a user who has a physical disability, such as restricted mobility or limited vision, to use software products successfully.