Mainframes are high-performance computers designed for massive throughput, reliability, and security. Understanding this architecture is essential for COBOL development.
Modern IBM mainframes (z Systems) can process billions of transactions daily while maintaining sub-second response times, making them ideal for COBOL applications handling critical business data.
COBOL programs can be developed in various environments, each with different advantages:
The choice of development environment often depends on organizational requirements, existing infrastructure, and developer preferences.
TSO (Time Sharing Option) and ISPF (Interactive System Productivity Facility) provide the traditional mainframe development environment for COBOL. Understanding this environment is fundamental even if using modern tools.
TSO is a command-line interface for interacting with the mainframe, allowing users to execute commands, run programs, manage datasets, and submit batch jobs.
12345ALLOCATE - Create new datasets DELETE - Remove datasets RENAME - Change dataset names SUBMIT - Submit JCL for execution LISTCAT - View catalog information
ISPF provides a menu-driven interface with panels for different functions:
The ISPF editor is used to create and modify COBOL programs with features like line commands, primary commands, syntax highlighting, and column indicators essential for traditional fixed-format COBOL.
COBOL programs on mainframes traditionally run in two modes:
Programs run without user interaction, processing data in bulk:
Programs interact with users in real-time:
Most enterprise COBOL applications involve a mix of batch and online programs working together to support business processes. Online programs typically run under transaction monitors like CICS or IMS, while batch programs are executed through JCL.
The mainframe environment involves several components working together:
A typical workflow involves JCL allocating necessary datasets and resources, executing a COBOL program, which then processes business data, with results stored in output datasets. This separation of concerns allows for flexible and reliable enterprise computing.
Match each mainframe component with its primary function:
Functions:
No, you don't necessarily need access to a mainframe. You can use alternatives like Micro Focus Visual COBOL, GnuCOBOL (open-source), IBM's Master the Mainframe program, or cloud-based z/OS systems. However, access to a real mainframe eventually becomes important for understanding the full context of enterprise COBOL development.
ISPF can present a learning curve for programmers accustomed to modern IDEs because it uses a character-based interface, relies on function keys and memorized commands, and lacks modern conveniences. However, most programmers become comfortable with it within a few weeks of regular use.
Yes, COBOL programs can run on distributed platforms using tools like Micro Focus Enterprise Server, GnuCOBOL, Veryant isCOBOL, and others. The portability depends on the program's use of mainframe-specific features, database access methods, and third-party products.