What is AS400, and how does it differ from other IBM systems?

What is AS/400?

AS/400 (Application System/400) is a midrange computer system developed by IBM in 1988, designed for businesses requiring high reliability, security, and scalability. It runs on IBM's proprietary OS/400 operating system (later evolved into IBM i) and is known for its integrated database (DB2 for i), object-based architecture, and seamless upward compatibility.

How AS/400 Differs from Other IBM Systems :

Feature	AS/400 (IBM i)	IBM Mainframes (zSeries)	IBM Power Systems (AIX/Linux)
OS	OS/400 (IBM i)	z/OS, z/VSE, z/VM	AIX (Unix), Linux
Architecture	Object-based, integrated DB	Batch-oriented, highly scalable	Unix-based, open-source friendly
Target Market	Midrange businesses	Large enterprises, financial institutions	Enterprise computing, AI, HPC
Database	DB2 for i (integrated)	DB2, IMS, others	DB2, Oracle, MySQL
Security	Built-in security, role-based	Extensive security layers	Unix/Linux-based security models
User Interface	Green screen (5250), web-enabled	Batch processing, CICS, TSO	GUI, SSH, terminal
Virtualization	Logical partitioning (LPAR)	PR/SM for LPARs	PowerVM for AIX/Linux

Key Differences :

Simplicity & Integration: AS/400 (IBM i) is known for its all-in-one system, including OS, database, security, and middleware, unlike mainframes and AIX/Linux systems, which often require separate configurations.
Object-Based Architecture: Unlike traditional Unix-based systems, IBM i uses an object-based file system, which enhances security and system integrity.
Backward Compatibility: IBM i systems maintain seamless compatibility with older applications, while mainframes and AIX systems may require more migration efforts.
Use Cases: AS/400 (IBM i) is widely used in industries like manufacturing, banking, and retail, whereas mainframes dominate high-volume transaction processing and AIX/Linux systems are used for cloud, AI, and enterprise applications.