IBM Power Systems

IBM System i

IBM System Storage and TotalStorage

IBM System i (IBM Power Systems)

System i, the most recent name of the platform formerly known as eServer iSeries, AS/400, and Application System/400, comprises a whole range of IBM servers with related operating systems and applications.

The first server of this type, produced in 1988, succeeded IBM System/38 architecture. The current models feature POWER6 processors.

„System i“ is an object-based system with an integrated DB2 relational database.

Success and longevity of AS/400 system can be attributed to its high-level instruction set (the TIMI layer), which allows the operating system and application programs to run on different types of hardware without the need for recompilation. This is conceptually somewhat similar to the virtual machine architecture of programming environments such as Java and .NET. The only difference is that this virtualisation is embedded into the very core of AS/400's design, thus making its applications binary-compatible across different processor families. Worth noting is the fact that with AS/400 System, TIMI instructions are not interpreted at runtime, but constitute an intermediate compile time step and are translated into the processor's instruction set as the final compilation step. The TIMI instructions are stored within the final program object, in addition to the executable machine instructions. Machine instructions are normally executed at run time. However, only when migrating from one processor architecture to another, using the save-restore method, are the old instructions discarded and the new ones generated based on the TIMI instructions.

Hardware-wise, AS/400 system can be described as an intelligent network of processing units, with each unit handling a specific task. For example, database queries are handled by processors designed for that particular task, without any intervention from the main processing unit. Similarly, interactive terminal sessions are managed by workstation processors. Consequently, even processors with relatively low processing speed and power do not pose a limiting factor for overall speed and robustness of the system as a whole. This architecture also allows for adjustments and customisation of the servers according to the clients' specific needs. For instance, if a server is to be used only for website hosting, it will not require terminal station processors, but it will need a more powerful subsystem and controllers, and more storage space.

„System i“ comes with i5/OS operating system (formerly OS/400), which is object- and library-based, including libraries with numerous functions designed for easy implementation by end-users in their operating environments. Besides i5/OS, the system supports simultaneous running of several instances of Linux, AIX, Lotus Domino, Microsoft Windows 2000 and Windows Server 2003 environments. While AIX, Linux and Lotus Domino are supported on the POWER processors, Windows is supported either on single-processor internal blade servers or externally-linked multiple-processor servers via IXA adapters.

The technology that enables simultaneous running of multiple operating systems is called LPAR. This technology facilitates optimal resource sharing (memory, processors, storage etc.) in such a way as to provide each partition with adequate resources, according to rules and priorities defined beforehand.

When it first appeared in 1988, AS/400 system represented a revolution in business IT environments. At that time, AS/400 offered a choice of 2500 business applications. Apart from the operating system, the server features a fast relational database, menu-driven interface, support for multiple user sessions, as well as for terminals, printers, communication, client-server and web-based applications. Each and every application can run on both the smallest single processor server and on the most powerful 64-processor servers.

Subsequent generations of iSeries and System i servers support modern ODBC and JDBC client-server technologies for database accessing from client applications written in Java or .NET.

„System i“ platform supports the following programming languages: RPG, assembly languages, C, C++, Pascal, Java, Smalltalk, COBOL, EGL, SQL, BASIC, PHP, PL/I and REXX. Several CASE tools are also available: AllFusion Plex, Synon, AS/SET, LANSA, ProGen Plus and Magic eDeveloper.

It also provides support for business applications written in traditional programming languages such as RPG, COBOL, and C, by means of external files, display files and object-oriented programming. It also supports Unix-like directory structure, Java, client-server technologies and integrated Apache server for multi-level applications.

When AS/400 first appeared, it ran on a special custom made CISC processor. This architecture was called IMPI and its instruction set was similar to those of IBM 370 systems. In 1994, CISC architecture was abandoned in favour of IBM's POWER-based RISC processors. The following is an overview of models and processing units by year in which they were launched: