TSO/E, ISPF, and UNIX System Services (USS): Interactive facilities of z/OS
The process of connecting to the mainframe
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The process of connecting to the mainframe
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Interacting with IBM z/OS using the TN3270 terminal remains a staple for mainframe professionals, despite the availability of modern methods like code editors. Typically, you begin by opening the TN3270 client to connect to TSO/E, the interface that enables multiple users to interact with the mainframe simultaneously. After logging in with your credentials, you access ISPF (Interactive System Productivity Facility), a menu-driven interface that allows you to navigate and manage various components of z/OS. Through ISPF panels, you can edit code, submit jobs, manage datasets, and monitor system activities. Upon the completion of your tasks, you can log off from TSO/E to end your session and disconnect from the mainframe. While newer tools offer more user-friendly features, the TN3270 terminal is a reliable and essential method for direct access to system resources.
3270 and TN3270 are key interfaces for connecting to z/OS. TN3270, or Telnet 3270, is emulator software that allows workstations to connect and log into z/OS systems. Understanding TN3270 is essential for z/OS users, as it emulates the functionality of the original 3270 display devices introduced in 1971. The 3270 devices used a character data stream protocol, which was designed for efficient data entry and retrieval, compensating for the limited network capabilities of the era. This protocol's efficiency continues to be valuable today, especially when fast interactive response times are needed on z/OS.
While TN3270 brings the 3270 interface to modern workstations, it does have some quirks, particularly around keyboard navigation. The original 3270 had a unique keyboard layout, and as keyboards evolved, differences such as the location of the 'Enter' key arose. In TN3270 emulators, the 'Enter' command (hex X'7D') is often mapped to the right 'Ctrl' key rather than the labeled 'Enter' key, but most emulators allow customization of these key mappings to fit user preferences.
TN3270 emulators offer various configuration options, including screen sizes, fonts, colors, and code pages, making them flexible tools for connecting to z/OS. They are used daily by support technicians, developers, and many back-office personnel for business transactions and production applications. The ability to customize login screens and cursor placements enhances user interaction with z/OS applications. TN3270’s speed, reliability, and customization options make it an indispensable tool for accessing z/OS environments, both now and in the future.
Watch the following video to learn 3270 and TN3270:
TSO is a command-line interface that’s an integral part of the z/OS operating system, offering a text-based way to interact with the system. While it may remind you of the DOS command prompt in Windows, TSO is far more powerful and is specifically tailored for mainframe operations.
Although TSO itself is text-based and does not support full-screen interactions, it’s commonly used alongside ISPF (Interactive System Productivity Facility), which enables full-screen applications for a more interactive user experience. TSO also plays a critical role behind the scenes, handling background tasks such as processing commands, scripts, and batch jobs.
Watch the following video to learn TSO/E in detail:
You might also find the introduction happening in 3270 helpful to match the concept to the actual practice:
Interactive System Productivity Facility (ISPF) is a multi-faceted development tool set for IBM Z®. It provides host-based software development, including software configuration management. Watch this video to get a brief idea about ISPF:
This short video provides a more details introduction to ISPF:
