Time Sharing Option (TSO) is an interactive time-sharing environment for IBM mainframe operating systems, including OS/360 MVT, OS/VS2 (SVS), MVS, OS/390, and z/OS.
TSO can also provide a Unix-style environment on OS/390 and z/OS via the UNIX System Services command shell, with or without ISPF.
TSO commands can be embedded in REXX and ooRexx execs or CLISTs, which can run interactively or in batch.
With the introduction of MVS in 1974, IBM made it a standard component of their top-end mainframe operating system.
It is common to run TSO in batch (as opposed to interactively): all the usual TSO line-mode interactive commands can be also executed via Job Control Language (JCL) by running any of the programs IKJEFT01, IKJEFT1A, and IKJEFT1B and supplying the line commands in a file pointed to by the SYSTSIN DD.