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AS/400- A primer

AS/400- A primer

Back on June 21st, 1988, IBM rolled out what it called Application System/400, or as it’s more popularly known, AS/400. It is a revolutionary computer system and was designed as a highly stable and secure system for offering a wide range of functionality to users.  Surprisingly, it is still used by a great deal of organizations, which demonstrates its usefulness till date. 

However, this forward thinking iconic server is fraught with some limitations and organizations relying on AS/400 systems often face problems with it. However, before we deep dive into the limitations and the benefits of AS/400, let’s have a look at its history.

A brief history of AS/400

As a member of the Midrange computers lineup from IBM, AS/400 was released in 1988, and ran the OS/400 operating system. Prior to this, IBM had launched its System38 in 1979 along with a complete product line-System3, System32, System34, System36. Later, AS400 was launched with the OS OS400 which was able to move the programs written for System34 and System36 to AS400. Lower cost but more powerful than its predecessors, the AS/400 was extremely successful at launch, with an estimated 111,000 installed by the end of 1990 and the associated revenue reaching $14 billion that year. While the first language that was supported by this system was RPG, subsequent versions of it followed as the system was enhanced.

In 2000, this old school giant was rebranded as the iSeries.Then in 2006, it was rebranded again as IBM System i. 2 years later, in 2008, the System i and System p product lines were combined into a new product line: IBM Power Systems. 

The table below shows a clear summary of the frequently changing hardwares and operating systems IN AS/400.

Having seen the frequently changing hardwares and OS of AS/400, let us now shed some light on its system architecture. 

System Architecture of IBM AS/400

Though easy to use, AS/400 has a complex internal architecture. It is integrated with hardware, software, security, a database and other components and can readily incorporate new technologies. It owns independent software and hardware sections due to which changes in one do not affect the other, which happens through the Machine Interface (MI).  

AS/400’s architecture is defined by five architectural principles:

Technology Independence: A key concept in the AS/400 platform is Technology Independent Machine Interface (TIMI). It is a platform-independent Instruction Set Architecture (ISA) that is compiled along with the native machine language instructions.

Software integration: OS/400 (now known as IBM i) is the native operating system of the AS/400 platform, and was the sole operating system supported on the original AS/400 hardware. Many of the advanced features associated with the AS/400 are implemented in the operating system as opposed to the underlying hardware, which changed significantly throughout the life of the AS/400 platform. Features include a RDBMS (DB2 for i), a menu-driven interface, support for multiple users, block-oriented terminal support (IBM 5250), and printers.

Object-based design: On IBM i, everything is an object be it a Printer Device, Programs, Web Services, APIs, Programs, Files, etc.

Single-Level Store: The term originally referred to what is now usually called virtual memory. So, the term Single-Level store is a computer storage term which has had two meanings. The two meanings are related in that in both, pages of memory may be in primary storage (RAM) or in secondary storage (disk), and that the physical location of a page is unimportant to a process.

Hardware Integration: Later generations of hardware are also capable of supporting various guest operating systems, including SSP, AIX, Linux, Microsoft Windows 2000 and Windows Server 2003. While OS/400, AIX, and Linux are supported on the POWER processors on LPARs (logical partitions), Windows is supported with either single-processor internal blade servers (IXS) or externally linked multiple-processor servers (IXA and iSCSI). SSP guests were supported using emulation from OS/400 V3R6 through V4R4 using the Advanced 36 Machine facility of the operating system, a feature distinct from the System/36 Environment compatibility layer which requires System/36 software to be recompiled.

What kind of programming languages can you use on AS/400?

Programming languages available for the AS/400 include RPG, assembly language, C, C++, Pascal, Java, EGL, Perl, Smalltalk, COBOL, SQL, BASIC, PHP, PL/I, Python and REXX. Several CASE tools are available: CA Plex (formerly AllFusion Plex), Synon, IBM Rational Business Developer Extension, Accelerator, LANSA, Uniface and GeneXus.

Important characteristics of IBM i/AS/400

Integrated components offerings: IBM i series is special as it comes integrated with many core functions and tools. For example, you will find web applications servers, web services server, a file system, DB2, i RDBMS and more. This integrated system is extremely robust and efficient as it can perform more than 300 tasks ranging from backup, recovery, communication to operations and security.

Administrator interface: While using Windows or Linux you might have come across a lot of tools that you need extra to boost your system’s administrative efforts. In the case of the IBM i system you can use IBM autonomic technologies to perform many low priority tasks.

PowerVM: The availability of PowerVM, a server virtualization software, in all IBM power systems avoids the use of large amounts of hardware. This reduces the complexity of administration as well as your energy costs. Power VM is a solution to minimize workload that helps clients control costs and improves overall performance, availability, flexibility and energy efficiency.

AS400 System Security Levels

OS400, the operating system in AS400 server, provided 5 security settings values from 10 to 50. Though value 10 setting has become obsolete and removed from the latest IBM i system, other 4 values remain and are used according to the business requirements of organizations.

The other levels range from 20 to 50 , with level 40 being the  default setting in all the IBM i systems.

Benefits of AS/400

Considering its stability, flexibility, security, and compatibility, the following are key reasons why the AS/400 i series platform is a great choice for business across domains:

AS/400 is upwardly compatible, this means that it helps to save money by eliminating expensive and time-consuming code migrations when platforms are upgraded.

Its reputation as a dated platform could hardly be further from the reality. Indeed, its good blend of native and open source programming languages provides modern and conventional stability.

Any security vulnerabilities or potential threats can be eliminated with the right AS/400 software application.

And when it comes to reliability, flexibility, and performance, AS/400 is at the top of the list. Almost all of the time, the platform is known to be functioning well.

Limitations of AS/400

Staffing: Since AS/400 systems are now decades old, the engineers who are managing these systems are close to retiring. This in turn is creating a shortage of skilled people who have the expertise to work on older languages such as RPG and COBOL.

UX/UI: Traditional green screens that users have to work on is yet another drawback of AS/400.

Operating System: OS 7.2, even 7.3 are becoming obsolete as newer OS versions like 7.4 are taking the iSeries world by storm. In April 2021, IBM officially sunset its Technology Refreshes (TRs) and Program Temporary Fixes ( PTFs) for version 7.2 users. Organizations with Power systems have the option of upgrading to 7.3 or 7.4 which has software support for years to come. But organizations using non-power systems either need to upgrade their hardware to accommodate newer OS or risk running into problems.

Security Concerns: Even though AS400/iSeries systems are super reliable, security threats while running an older application, database or OS version can make your legacy systems vulnerable to threats.

Lack of Integration: Applications running on iSeries/Power systems are isolated from the other software due to lack of integration.

Is AS/400 still relevant?

The short answer is YES and industries like finance, logistics, insurance, manufacturing, transportation etc. are using this legacy technology in a modernized way. According to Enlyft around 35000+ companies are using IBM i and most of them are in the United States. As per Enlyft,  IBM AS/400 has a market share of about 36.03%

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With that being said, AS400 iSeries platforms are still in demand due to the following features:


Businesses can quickly start with a 4-core server at a low cost. Further, we can upgrade the 256 core machines with changing business requirements. So, the As 400 iSeries platform is best for all company sizes.

Logical Partitioning (LPAR)

We can run multiple operating systems consecutively on a single IBM i device using this feature. It allows us to create separate partitions for each operating system. Moreover, it ensures that no one OS uses the space or resources of another.

Software Integration And IBM i Application Modernization

AS/400/ IBM i platform supports all existing programs. In addition, we can integrate native and open-source development languages (SQL, Java, .NET, PHP, and C++) in the legacy applications for application modernization.

Wrapping it up.

The AS/400 system was introduced in the ’80s. That’s why most people assume that the AS/400 is considered dead now, but we do not agree with this assumption. The IBM i series, AS/400 mid-range lines of systems, has undergone many updates and revisions and in spite of all these rebranding attempts, the IBM AS/400 platform is still an important element of many of the world’s top organizations. 

However what is required now is augmenting the capabilities of AS/400 by connecting them to the modern world through code refactoring and thereby helping organizations maintain their AS/400 investments. Enhancing the capabilities of AS/400 via re-factoring can help organizations reduce costs and risks while helping them become digital to the core. AS/400 augmentation can even help businesses leverage their core assets and accelerate innovation. 

To know more about AS/400 augmentation and the immense benefits it can offer to your business,  stay tuned for our next blog. 

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