Chapter 18. Procedure Language REXX

The REstructured eXtended eXecutor language, or REXX language, is a versatile, easy to use structured procedure language that is part of:

VM/ESA

VSE/ESA

TSO/E

REXX was designed as a replacement for the EXEC and EXEC2 languages that provided a way to bundle Conversational Monitor System (CMS) commands together. REXX is an extremely versatile programming language in that it can be intermixed with commands to host environments, it provides powerful functions, and it has extensive mathematical capabilities.

18.1 REXX and VM/ESA

By far, the most vital role REXX plays is as a procedural language for VM/ESA. That means a REXX procedure can be a kind of script for VM/ESA to follow. By using REXX, you can reduce long and complex or repetitious tasks to a single command or procedure that can be run from CMS.

REXX is a built-in feature of VM/ESA, so there is no installation process or separate environment. Any REXX procedure can call CMS commands, XEDIT macros, other subcommand environments, GCS and so on.

18.2 REXX and VSE/ESA

REXX programs can do many tasks, including the automation of VSE/Operations. For example, if you use the JCL EXEC command to call a REXX program, you can leave JCL statements on the stack for VSE/ESA to process. This enables you to insert JCL statements or data into the current job stream. REXX programs can run in any partition. They can communicate with POWER through the Spool Access Support interface.

REXX/VSE is available for all VSE/ESA 2.1 and higher and is integrated closely into the VSE/ESA central functions. It is implemented through:

The REXX/VSE interpreter

The Library for REXX/370 in REXX/VSE

18.3 REXX and TSO/E

The TSO/E implementation of the REXX language allows REXX execs to run in any MVS address space. You can write a REXX exec that includes TSO/E services and run it in a TSO/E address space, or you can write an application in REXX to run outside of a TSO/E address space. REXX runs in an OS/390 system in different environments: MVS, NetView, OE shell scripts, ... .

© Copyright IBM Corp. 1998

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OS/390 specifications

IBM OS/390, a versatile operating system, was a cornerstone in enterprise environments and played a pivotal role in mainframe computing. Released in the mid-1990s, OS/390 combined the strengths of IBM's MVS (Multiple Virtual Storage) with new features and enhancements, targeting scalability, reliability, and performance in demanding business applications.

One of the key features of OS/390 was its robust support for multiple users and processes. The system allowed thousands of concurrent users to access applications and data, ensuring high availability and minimizing downtime—a critical requirement for many large organizations. This scalability was supported through various enhancements in memory management and processor scheduling, enabling optimal resource allocation across diverse workloads.

OS/390 was known for its superior workload management capabilities. The Workload Manager (WLM) component allowed administrators to define service policies, specifying how system resources would be allocated according to the priority of tasks. This ensured that critical business processes received the necessary resources while less critical tasks were managed more flexibly.

Another significant characteristic of OS/390 was its commitment to security. The operating system provided comprehensive security features, including user authentication, data encryption, and auditing capabilities. This focus on security was vital for organizations handling sensitive data, ensuring compliance with regulations and safeguarding against unauthorized access.

OS/390 also supported advanced technologies that facilitated integration and development. The system included features like the IBM CICS (Customer Information Control System) for transaction processing and IMS (Information Management System) for database management. These technologies allowed organizations to build robust, high-performance applications tailored to specific business needs.

The ease of network integration was another strength of OS/390. With the advent of the Internet and global connectivity, OS/390 systems could easily interface with various network protocols, enabling businesses to operate in a connected world. This inclusion paved the way for many organizations to expand their capabilities and offer new services, driving digital transformation.

In conclusion, IBM OS/390 represented a significant advancement in mainframe technology, combining scalability, security, and robust workload management. Its rich feature set and support for critical enterprise applications solidified its role as a vital component of many organizations' IT infrastructures, ensuring they could meet their operational challenges head-on while supporting future growth. As technology continues to evolve, the legacy of OS/390 remains influential in the realm of computing.