AS/400

AS/400
Name	AS/400
Developer	IBM
Family	IBM midrange
Type	Midrange server
Introduced	1988
Discontinued	evolved into IBM i
Cpu	PowerPC/POWER architecture (later)
Os	OS/400 (IBM i)
Predecessor	System/36, System/38
Successor	IBM i on Power Systems

AS/400

The AS/400 was a family of IBM midrange computer systems introduced as an integrated hardware and software platform. It combined innovations from System/36, System/38, and projects at IBM Rochester with influences from IBM System/3 and the IBM System/36 lineage, aiming to serve enterprises running transactional workloads for organizations such as JPMorgan Chase, Walmart, Delta Air Lines, Bank of America. The platform gained adoption across sectors including manufacturing, retail, banking, healthcare and was notable for longevity alongside systems like the VAX and UNIVAC families.

History

IBM unveiled the system in 1988 as part of a lineage extending from System/38 and System/36, developed at facilities including IBM Rochester and influenced by design teams with ties to IBM Research and projects associated with Project Eagle and Fortress. Early marketing positioned the machine against offerings from DEC, HP, UNIVAC and smaller vendors such as Data General and Tandem Computers. Adoption by major enterprises like Procter & Gamble, British Airways, General Motors, Siemens and AT&T reflected its strength in transaction processing compared with architectures from Sun Microsystems and Oracle Corporation-driven database servers. Over time, the product strategy intersected with initiatives at Lotus Development Corporation and standards bodies including IEEE and X/Open as IBM migrated technology toward the POWER instruction set and rebranded server lines culminating in Power Systems.

Architecture

The system used an object-based architecture derived from the System/38 architecture, combining integrated database concepts, single-level storage and object-oriented control structures influenced by research at IBM Research and advances in RISC designs like POWER. The instruction set and microarchitecture evolved toward the POWER ISA family, sharing lineage with processors used by RS/6000 systems and later Power Systems servers. Key components mirrored concepts from platforms such as VAX, MIPS and SPARC insofar as CPU, memory and I/O subsystems conformed to enterprise reliability and availability patterns seen in systems by Tandem Computers and Sun Microsystems. The design emphasized integrated serviceability similar to practices at Hewlett-Packard and Oracle enterprises.

Operating System and Software

The original operating environment, OS/400, incorporated integrated database structures and single-level storage influenced by research from IBM Research and design philosophy akin to systems like Multics and some ideas from VMS. Software stacks included business applications, middleware and development tools from vendors such as IBM Rational, CA Technologies, SAP SE, Oracle Corporation, Microsoft (through interoperability tools), BMC Software and independent software vendors serving sectors like finance and logistics. Development languages and environments supported on the platform included RPG, COBOL, C and later Java, with tooling integration from Eclipse-based tools and products from IBM Software Group.

Hardware Models and Evolution

Models evolved from the original midrange cabinets to rack-mounted and blade configurations paralleling shifts seen at Sun Microsystems and HP Enterprise. The hardware roadmap moved from proprietary CPUs toward the POWER and PowerPC families, aligning with processors used by RS/6000 and later Power Systems offerings. Storage and I/O subsystems adopted enterprise-class technologies comparable to arrays from EMC Corporation and controllers modeled after designs in Fibre Channel SANs. Maintenance and virtualization capabilities mirrored trends from VMware and IBM VM efforts, while clustering and high-availability implementations drew upon approaches used by Tandem Computers and Stratus Technologies.

Applications and Use Cases

Enterprises used the platform for core transactional systems, ERP deployments, supply-chain management and point-of-sale applications, with prominent implementations at companies such as Walgreens, Target Corporation, Tesco, Citigroup and HSBC. The platform supported workloads spanning retail, banking, manufacturing and distribution and hosted packaged software from vendors like SAP SE, PeopleSoft (now part of Oracle Corporation), JD Edwards and numerous regional ISVs. Its integration of database and OS made it attractive for heavy OLTP use cases seen in payment processing systems at Visa and Mastercard networks and logistics operations used by FedEx and UPS.

Legacy and Influence

The platform’s architectural choices—object-based OS structures, integrated database, single-level storage and long lifecycle support—affected subsequent IBM strategies including IBM i and influenced practices at Oracle Corporation and Microsoft around platform integration. Its user base and software ecosystem fostered third-party vendors like Rocket Software, LANSA and BMC Software. Academic and industry discussions at conferences held by ACM, IEEE and USENIX examined its reliability and maintainability features alongside systems like VAX/VMS and UNIX System V. Many enterprises continue migration, modernization and interoperability efforts involving Linux, AIX, Windows Server and cloud providers such as AWS, Microsoft Azure and Google Cloud Platform while legacy knowledge persists in professional communities and training programs connected to institutions like IBM Training and enterprise IT consultancies including Accenture and Deloitte.

Category:IBM hardware