computer science

OS/390

OS/390 is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand OS/390 rather than just read about it. In short: OS/390 is an IBM operating system for the System/390 IBM mainframe computers. 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.

Key takeaways

OS/390 belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect OS/390 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of OS/390 from memory before moving on to harder problems.

Reference excerpt

OS/390 is an IBM operating system for the System/390 IBM mainframe computers.

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) – Provides access methods to enable I/O to, e.g., Direct access storage device subsystems, printers, tape; provides utilities and program management Job Entry Subsystem (JES) – Provides the ability to submit batch work and manage print IBM Communications Server – 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 Reports and Program temporary fixes) 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

See also OS/360 MVS z/OS z/TPF z/VM z/VSE Linux on IBM Z

References

Worked examples

Example 1 — a first encounter with OS/390

Start with the simplest possible case. Write down what OS/390 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to OS/390 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about OS/390 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of OS/390

In research: OS/390 appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses OS/390 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: OS/390 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1995 software, IBM ESA/390 operating systems, IBM mainframe operating systems, so understanding it makes those chapters shorter.
In everyday life: Look for OS/390 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study OS/390 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what OS/390 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain OS/390 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is OS/390 in simple terms?

OS/390 is an IBM operating system for the System/390 IBM mainframe computers. 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.

Why does OS/390 matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study OS/390?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on OS/390.