CBT - Chicago Board of Trade tape

Enhanced Definition

The CBT tape is a widely recognized, historical, and continuously updated collection of public domain software, utilities, and tools for IBM mainframe systems, primarily z/OS and its predecessors. It originated from the Chicago Board of Trade, where mainframe professionals collaboratively shared useful programs, macros, and system enhancements.

Key Characteristics

- Public Domain Software: All content within the CBT collection is freely available, can be used without licensing fees, and is often provided with source code for modification.
- User-Contributed: The collection is maintained and expanded through voluntary contributions from the global mainframe community, reflecting practical solutions to real-world operational challenges.
- Extensive Utilities: It contains a vast array of tools, including system utilities, development aids (e.g., ISPF macros, REXX execs), performance monitors, security tools, dataset management utilities, and sample code.
- Historical Significance: Represents a long-standing tradition of knowledge sharing and collaboration within the mainframe ecosystem, predating modern open-source repositories.
- Distribution Format: While historically distributed on magnetic tapes, it is now primarily available as downloadable datasets (e.g., PDS, PDSE) via FTP or web, often as a single large archive containing numerous individual members.
- Source Code Availability: Many entries include full source code (e.g., Assembler, PL/I, COBOL, REXX), enabling users to understand, customize, and learn from the implementations.

Use Cases

- System Administration: Finding specialized utilities for tasks like dataset cleanup, system monitoring, security auditing, or managing system resources that are not part of standard IBM offerings.
- Application Development: Utilizing ISPF macros, REXX execs, or sample code to automate development tasks, enhance ISPF productivity, or learn specific programming techniques.
- Problem Solving: Searching for existing tools or solutions to address specific mainframe operational or development challenges, leveraging the collective experience of the community.
- Education and Learning: Studying the source code of various utilities to gain deeper insights into z/OS internals, mainframe programming paradigms, or specific system APIs.
- Legacy System Support: Accessing tools or information that might be particularly useful for maintaining or understanding older z/OS versions or specific mainframe configurations.

Related Concepts

The CBT tape can be seen as an early form of community-driven open source for the mainframe, complementing commercial software and IBM's own offerings. It often provides niche utilities that extend the capabilities of core z/OS components, ISPF, JCL, and various programming languages like Assembler and REXX. It demonstrates the ingenuity of mainframe professionals in building tools to enhance productivity, automate tasks, and solve complex system problems, often leveraging SVCs, EXCP, and other low-level system interfaces.

Best Practices:

Verify Source: Always download the CBT tape from official or well-known, trusted sources to ensure the integrity and authenticity of the code.
Test Thoroughly: Before deploying any CBT utility in a production environment, rigorously test it in a development or test LPAR to confirm its stability, compatibility, and intended functionality.
Review Source Code: For critical utilities, review the provided source code to understand its logic, potential resource consumption, and any security implications before execution.
Understand Usage Notes: Pay attention to any specific documentation or usage notes associated with individual CBT entries, as some might have particular requirements or limitations.
Backup and Version Control: When modifying CBT utilities, always maintain backups of the original files and consider using internal version control practices to track changes.