computer science

NonStop (server computers)

NonStop (server computers) 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 NonStop (server computers) rather than just read about it. In short: NonStop is a series of server computers introduced to market in 1976 by Tandem Computers Incorporated, beginning with the NonStop product line. It was followed by the Tandem Integrity NonStop line of lock-step fault-tolerant computers, now defunct (not to be confused with the later and much different Hewlett-Packard Integrity product line extension).

Key takeaways

NonStop (server computers) 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 NonStop (server computers) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NonStop (server computers) from memory before moving on to harder problems.

Reference excerpt

NonStop is a series of server computers introduced to market in 1976 by Tandem Computers Incorporated, beginning with the NonStop product line. It was followed by the Tandem Integrity NonStop line of lock-step fault-tolerant computers, now defunct (not to be confused with the later and much different Hewlett-Packard Integrity product line extension). The original NonStop product line is currently offered by Hewlett Packard Enterprise since Hewlett-Packard Company's split in 2015. Because NonStop systems are based on an integrated hardware/software stack, Tandem and later HPE also developed the NonStop OS operating system for them. NonStop systems are, to an extent, self-healing. To circumvent single points of failure, they are equipped with almost all redundant components. When a mainline component fails, the system automatically falls back to the backup. These systems can be used by banks, stock exchanges, payment applications, retail companies, energy and utility services, healthcare organizations, manufacturers, telecommunication providers, transportation, and other enterprises requiring extremely high uptime. In 2002, 95% of worldwide stock transactions and two-thirds of credit card transactions were handled by NonStop computers.

History Originally introduced in 1976 by Tandem Computers Inc., the line was later owned by Compaq (from 1997), Hewlett-Packard Company (from 2003) and Hewlett Packard Enterprise (since 2015). In 2005, the HP Integrity "NonStop i" (or TNS/E) servers, based on Intel Itanium microprocessors, was introduced. In 2014, the first "NonStop X" (or TNS/X) systems, based on Intel x86-64 processors, were introduced. Sales of the Itanium-based systems ended in July 2020. Early NonStop applications had to be specifically coded for fault tolerance. That requirement was removed in 1983 with the introduction of the Transaction Monitoring Facility (TMF), along with Pathway transaction management software and SCOBOL applications (or, later, NonStop Tuxedo transaction management software), which handles the various aspects of fault tolerance on the system level.

Software NonStop OS is a message-based operating system designed for fault tolerance. It works with process pairs and ensures that backup processes on redundant CPUs take over in case of a process or CPU failure. Data integrity is maintained during those takeovers; no transactions or data are lost or corrupted. The operating system includes the Guardian layer, which is a low-level component of the operating system, and the Open System Services (OSS) personality which runs atop this layer, which implements a Unix-like interface for other components of the OS to use. The operating system and application are designed to support the fault tolerant hardware. The operating system monitors the status of all components, switching control as necessary to maintain operations. Software programs can be written as continuously available programs using a pair of processes where one process performs all the primary processing and the other serves as a "hot backup", receiving updates to data whenever the primary reaches a critical point in processing. Should the primary stop, the backup steps in to resume execution using the current transaction. The systems support relational database management systems like NonStop SQL and hierarchical databases such as Enscribe. Languages supported include Java, C, C++, COBOL, SCOBOL (Screen COBOL), Transaction Application Language (TAL), etc. It uses the scripting and job control language TACL (Tandem Advanced Command Language), and is written in TAL and C.

Hardware

The HPE Integrity NonStop computers are a line of fault-tolerant, message-based server computers based on the Intel Xeon processor platform, and optimized for transaction processing. Average availability levels of 99.999% have been observed. NonStop systems have a massively parallel processing (MPP) architecture that provides linear scalability. Each CPU runs a copy of the operating system, and systems can be expanded to over 4000 CPUs. This is a shared-nothing architecture—also known as loosely coupled multiprocessing. Due to the integrated hardware/software stack and a single system image, system management requirements for NonStop systems are simplified. In most deployments there is a single system image, not a complex server farm. Most customers also have a backup server in a remote location for IT disaster recovery. There are standard products to keep the data of the production and the backup server synchronized, for example, HPE's Remote Database Facility (RDF), hence there is fast takeover and little to no data loss in a disaster situation with the production server being disabled or destroyed. HP also developed a data warehouse and business intelligence server line, HP Neoview, based on the NonStop line. It acted as a database server, providing NonStop OS and NonStop SQL, but lacked the transaction processing functionality of the original NonStop systems. The line was retired, and no longer marketed, as of 24 January 2011.

See also List of compilers – includes some compilers for NonStop Master-checker Reliability engineering Stratus Technologies

References

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with NonStop (server computers)

Start with the simplest possible case. Write down what NonStop (server computers) 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 NonStop (server computers) 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 NonStop (server computers) 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 NonStop (server computers)

In research: NonStop (server computers) 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 NonStop (server computers) 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: NonStop (server computers) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 1976, Computer architecture, Fault-tolerant computer systems, so understanding it makes those chapters shorter.
In everyday life: Look for NonStop (server computers) 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study NonStop (server computers) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NonStop (server computers) 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 NonStop (server computers) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NonStop (server computers) in simple terms?

Why does NonStop (server computers) 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 NonStop (server computers)?

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 NonStop (server computers).