Time Sharing Option
Encyclopedia
In computing
, 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
.
login sessions. Time-sharing
means that many persons can access the operating system concurrently, while unaware that others are also accessing the operating system. It appears to each TSO user that they are the only user on the system.
TSO is most commonly used by mainframe system administrator
s and programmers. It provides:
The name "Time Sharing Option" derives from the fact that, when it was originally introduced in 1971, IBM considered time-sharing an "optional feature," as compared to standard batch processing
, and hence offered TSO as an option for OS/360 MVT]. With the introduction of MVS in 1974, IBM made it a standard component of their top-end mainframe operating system. TSO/E ("Time Sharing Option/Extensions") is a set of extensions to the original TSO. TSO/E is a base element of z/OS. Before z/OS, TSO Extensions (TSO/E) was an element of OS/390 and was a licensed program for the MVS and MVS/ESA System Products. Since all z/OS installations usually have both TSO and TSO/E functions installed, it is normal to refer to both TSO and TSO/E as "TSO".
TSO interacts with users in either a line-by-line mode or in a full screen, menu-driven mode. In the line-by-line mode, the user enters commands by typing them in at the keyboard; in turn, the system interprets the commands, and then displays responses on the terminal screen. But most mainframe interaction is actually via ISPF
, which allows for customized menu-driven interaction. This combination is called TSO/ISPF. 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
execs or CLIST
s, which can run interactively or in batch.
(JCL) by running any of the programs
Batch execution of TSO is one way to allow an IBM mainframe application to access DB2
resources.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, Time Sharing Option (TSO) is an interactive time-sharing
Time-sharing
Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
environment for IBM mainframe
IBM mainframe
IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...
operating systems, including OS/360 MVT, OS/VS2 (SVS)
OS/VS2 (SVS)
Single Virtual Storage refers to Release 1 of Operating System/Virtual Storage 2 ; it is the successor system to the MVTBut not 65MP option of Operating System/360...
, MVS
MVS
Multiple Virtual Storage, more commonly called MVS, was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers...
, OS/390
OS/390
OS/390 is an IBM operating system for the System/390 IBM mainframe computers.OS/390 was introduced in late 1995 in an effort, led by the late Randy Stelman, to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional MVS operating system package...
, and z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
.
Overview
TSO fulfills a similar purpose to UnixUnix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
login sessions. Time-sharing
Time-sharing
Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
means that many persons can access the operating system concurrently, while unaware that others are also accessing the operating system. It appears to each TSO user that they are the only user on the system.
TSO is most commonly used by mainframe system administrator
System administrator
A system administrator, IT systems administrator, systems administrator, or sysadmin is a person employed to maintain and operate a computer system and/or network...
s and programmers. It provides:
- A text editorText editorA text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....
- Batch job support, including completion notification
- DebuggerDebuggerA debugger or debugging tool is a computer program that is used to test and debug other programs . The code to be examined might alternatively be running on an instruction set simulator , a technique that allows great power in its ability to halt when specific conditions are encountered but which...
s for some programming languages used on System/360System/360The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...
and later IBM mainframes - Support for other vendors' end-user applications, for example for querying IMSInformation Management SystemIBM Information Management System is a joint hierarchical database and information management system with extensive transaction processing capabilities.- History :...
and DB2IBM DB2The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...
databases
The name "Time Sharing Option" derives from the fact that, when it was originally introduced in 1971, IBM considered time-sharing an "optional feature," as compared to standard batch processing
Batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...
, and hence offered TSO as an option for OS/360 MVT]. With the introduction of MVS in 1974, IBM made it a standard component of their top-end mainframe operating system. TSO/E ("Time Sharing Option/Extensions") is a set of extensions to the original TSO. TSO/E is a base element of z/OS. Before z/OS, TSO Extensions (TSO/E) was an element of OS/390 and was a licensed program for the MVS and MVS/ESA System Products. Since all z/OS installations usually have both TSO and TSO/E functions installed, it is normal to refer to both TSO and TSO/E as "TSO".
TSO interacts with users in either a line-by-line mode or in a full screen, menu-driven mode. In the line-by-line mode, the user enters commands by typing them in at the keyboard; in turn, the system interprets the commands, and then displays responses on the terminal screen. But most mainframe interaction is actually via ISPF
ISPF
In computing, Interactive System Productivity Facility is a software product for the z/OS operating system that runs on IBM mainframes...
, which allows for customized menu-driven interaction. This combination is called TSO/ISPF. TSO can also provide a Unix-style environment on OS/390 and z/OS via the UNIX System Services
UNIX System Services
UNIX System Services is a required, included component of z/OS. USS is a certified UNIX implementation optimized for mainframe architecture. It is the first UNIX 95 to not be derived from the AT&T source code...
command shell
Shell (computing)
A shell is a piece of software that provides an interface for users of an operating system which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web...
, with or without ISPF.
TSO commands can be embedded in REXX
REXX
REXX is an interpreted programming language that was developed at IBM. It is a structured high-level programming language that was designed to be both easy to learn and easy to read...
execs or CLIST
CLIST
CLIST is a procedural programming language for TSO in MVS systems. It originated in OS/360 Release 20 and has assumed a secondary role since the availability of Rexx in TSO/E Version 2....
s, which can run interactively or in batch.
TSO in batch
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 LanguageJob Control Language
Job Control Language is a scripting language used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem....
(JCL) by running any of the programs
IKJEFT01, IKJEFT1A, or IKJEFT1B and supplying the line commands in a file pointed to by the SYSTSIN DD. The primary difference between the three programs is their handling of return codes from the executed commands.Batch execution of TSO is one way to allow an IBM mainframe application to access DB2
IBM DB2
The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...
resources.
See also
- History of IBM mainframe operating systemsHistory of IBM mainframe operating systemsThe history of operating systems running on IBM mainframes is a notable chapter of history of mainframe operating systems, because of IBM's long-standing position as the world's largest hardware supplier of mainframe computers....
- Michigan Terminal SystemMichigan Terminal SystemThe Michigan Terminal System is one of the first time-sharing computer operating systems. Initially developed in 1967 at the University of Michigan for use on IBM S/360-67, S/370 and compatible mainframe computers, it was developed and used by a consortium of eight universities in the United...
- MUSIC/SPMUSIC/SPMUSIC/SP was developed at McGill University in the 1970s from an early IBM time-sharing system called RAX...
- ORVYL and WYLBUR
Further reading
The books: MVS TSO, Part 1: Concepts and ISPF, Second Edition and, MVS TSO, Part 2: Commands And Procedures, Second Edition both by Doug Lowe, and published by Mike Murach & Associates, Inc., 1991External links
- Several TSO Manuals from the early 1970s, available from the BitSavers.org archive