TSO
Time Sharing Option: the interactive login environment on z/OS, where you get a command prompt and a session of your own.
Also written Time Sharing Option, TSO/E
TSO stands for Time Sharing Option. It is the part of z/OS that lets people log on and work interactively, each with their own session, sharing the system at the same time. When you connect to a mainframe with a user ID and password, you are logging on to TSO.
On its own, TSO gives you a plain command line. You can type commands to list datasets, allocate space, run programs, send messages and submit jobs. It is capable but stark, and few people spend long there.
In practice almost everyone starts ISPF immediately after logging on, which puts a full-screen menu-driven interface on top of TSO. The commands are still TSO commands underneath; ISPF just gives them screens, panels and an editor.
The name reflects its history. In the 1970s, "time sharing" was the novel idea that several people could use one computer interactively at once. The name stuck, and TSO is still the front door to a z/OS system today.
Related terms
- ISPFThe full-screen, menu-driven workbench most people use to do their day-to-day work on z/OS.
- LogonSigning on to a mainframe system with a user ID and password to start an interactive session.
- TSO commandA command typed at a TSO prompt or on an ISPF command line to ask the system to do something directly.
- SDSFThe tool for looking at what jobs are running, what has finished, and what output they produced.
- z/OSThe main operating system that runs on IBM mainframes, in the same way Windows or Linux runs on a laptop or server.