View source for OS/390

{{Short description|Operating system for IBM mainframes}}
{{Use American English |date=February 2024}}
{{Use mdy dates |date=February 2024}}
{{More citations needed |date=February 2024}}
{{Infobox OS
| name                   = OS/390<!-- Name of program or distribution -->
| logo                   = IBM logo.svg
| logo caption           = 
| logo size              = 120px
| logo alt               = 
| screenshot             = <!-- filename only (no wikilink, no Image:/File:) -->
| caption                = 
| screenshot_size        = 
| screenshot_alt         = 
| collapsible            = 
| version of             = <!-- For articles about releases of operating systems ONLY -->
| developer              = [[IBM]]<!-- Name of main developer or sponsor-->
| family                 = [[MVS]]<!-- "Unix-like" or "Microsoft Windows" -->
| working state          = Discontinued<!-- "Current", "Discontinued" (operating systems), or "No longer supported" (releases) -->
| source model           = <!-- "Open source", "Closed source", or "Shared source" -->
| released               = {{Start date and age|1995}}
| discontinued           = <!-- DON'T use this for articles about releases of operating systems -->
| RTM date               = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->
| GA date                = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} ONLY for articles about OS releases -->
| latest release version = 
| latest release date    = 
| latest preview version = 
| latest preview date    = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} -->
| marketing target       = [[IBM mainframes|IBM mainframe computers]]
| programmed in          = 
| language               = [[English language|English]]<!-- Supported human languages (English, French, Italian, Arabic, ...) -->
| update model           = <!-- APT, Windows Update, etc. -->
| package manager        = <!-- dpkg, rpm, Windows installer, etc. -->
| supported platforms    = [[System/390]]<!-- IA-32, x64, Itanium, ARM, etc. -->
| kernel type            = <!-- Hybrid, Monolithic, Microkernel, Exokernel, Nanokernel, etc. -->
| userland               = 
| ui                     = 
| license                = [[Proprietary software|Proprietary]]
| preceded by            = 
| succeeded by           = [[z/OS]]
| website                = <!-- {{URL|www.example.org}} -->
| support status         = <!-- For articles about releases of operating systems ONLY -->
| other articles         = 
| prog_language          = 
}}
{{History of IBM mainframe operating systems|os}}
'''OS/390''' is an [[IBM]] [[operating system]] for the [[System/390]] [[IBM mainframes|IBM mainframe computers]].<ref name="ibm" />

==Overview==
OS/390 was introduced in late 1995 in an effort to simplify the packaging and ordering for the key, entitled elements needed to complete a fully functional [[Multiple Virtual Storage]] (MVS) operating system package.  These elements included, but were not limited to:

*Data Facility Storage Management Subsystem Data Facility Product (DFP){{snd}}Provides [[access method]]s to enable I/O to, e.g., [[Direct access storage device]] subsystems, printers, tape; provides utilities and program management
*[[Job Entry Subsystem 2/3|Job Entry Subsystem]] (JES){{snd}}Provides the ability to submit batch work and manage print
*[[IBM Communications Server]]{{snd}}Provides [[Virtual Telecommunications Access Method]] (VTAM) and [[TCP/IP]] communications protocols

An additional benefit of the OS/390 packaging concept was to improve [[reliability, availability and serviceability]] (RAS) for the operating system, as the number of different combinations of elements that a customer could order and run was drastically reduced.  This reduced the overall time required for customers to test and deploy the operating system in their environments, as well as reducing the number of customer-reported problems, errors ([[Authorized Program Analysis Report]]s and [[Program temporary fix]]es) arising from the variances in element levels.

In December 2001 IBM extended OS/390 to include support for 64-bit [[zSeries]] processors and added various other improvements, and the result is now named [[z/OS]]. IBM ended support for the older OS/390-branded versions in late 2004.

==OS/390 Releases==
{{main|OS/360 and successors#Timeline}}
<!-- To edit this table go to: https://en.wikipedia.org/wiki/Template:Releases_OS/390 -->
{{Releases OS/390}}

==See also==
* [[OS/360]]
* [[MVS]]
* [[z/OS]]
* [[z/TPF]]
* [[z/VM]]
* [[z/VSE]]
* [[Linux on IBM Z]]

== References ==
{{reflist |refs=
<ref name="ibm">{{cite web |title= The IBM System/390 |first=Stewart |last=Alsop |website=IBM |url= https://www.ibm.com/history/system-390 |access-date=2024-02-06 }}</ref>
}}

{{IBM operating systems}}

{{DEFAULTSORT:Os 390}}
[[Category:IBM mainframe operating systems]]
[[Category:IBM ESA/390 operating systems]]
[[Category:1995 software]]

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