The AS400, also known as the IBM iSeries or IBM Power Systems, remains a robust and versatile computer platform that serves as the backbone for many critical business operations. Its well-deserved reputation for reliability and security makes it a trusted choice for organizations of all sizes. If you're tasked with developing applications for the AS400, this comprehensive guide will equip you with the knowledge you need to navigate the process effectively.

Understanding the AS400 Landscape

The AS400 is an integrated system, meaning hardware, software, and networking components are tightly coupled to deliver a secure and reliable environment. This focus on integration simplifies IT management and enhances application performance. While the core AS400 is no longer actively sold by IBM, the company remains committed to supporting existing systems and offers migration paths to its modern IBM Power Systems lineup.

AS400 Application Development Tools

A variety of AS400 Application development tools cater to different programming languages and skill sets. Here's a look at some of the most popular options:

• RPG (Report Program Generator): A long-standing AS400 mainstay, RPG is a COBOL-derived language known for its ease of use and data handling capabilities. Many core AS400 applications are written in RPG.

• COBOL: This industry-standard language is well-suited for business applications that require extensive data manipulation.

• CL (Control Language): Primarily used for system administration tasks and automating processes, CL offers a powerful way to interact with the AS400 environment.

• Java: The AS400 offers a robust Java development environment, enabling you to leverage this widely-used object-oriented language for modern application development.

• ILE (Integrated Language Environment): A key component of the AS400's development environment, ILE allows programmers to use different languages (RPG, COBOL, CL) within a single program, improving code modularity and maintainability.

Planning and Design for AS400 Applications

Before diving into code, meticulous planning is crucial. Here are some key aspects to consider:

• Business Requirements: Clearly define the problem your application aims to solve and the specific functionalities it will deliver.

• User Interface (UI): Determine the type of UI (character-based, graphical) that best suits your application and target users. Modern AS400 environments support web-based UIs for broader accessibility.

• Data Model: Design a robust data model that efficiently stores and manages the information your application utilizes.

• Security: Integrate security best practices from the outset to safeguard sensitive data and ensure user access controls are in place.

Developing and Testing AS400 Applications

Once the plan is established, development can commence. Here are some key considerations:

• Coding Standards: Adhere to established coding standards to ensure code consistency, readability, and maintainability.

• Code Reviews: Implement a code review process to identify and rectify errors early in the development cycle.

• Unit Testing: Develop unit tests to verify the functionality of individual program modules.

• Integration Testing: Test how different program modules interact with each other to ensure a seamless user experience.

• System Testing: Perform comprehensive system testing to identify and resolve any issues before deployment.

Deployment and Maintenance of AS400 Applications

Following successful testing, it's time to deploy your application to the production environment. Here's what to keep in mind:

• Change Management: Follow a structured change management process to minimize disruption during deployment.

• Documentation: Create comprehensive user and technical documentation for future reference and troubleshooting.

• Monitoring: Implement application monitoring to identify and address any performance issues or errors that may arise.

• Maintenance: Regularly maintain your application to address evolving business needs, security patches, and bug fixes.

Additional Considerations for Modern AS400 Development

While the AS400 offers a mature and stable platform, here are some factors to consider for modern application development:

• API Integration: AS400 applications can integrate with external systems and services through APIs, enabling data exchange and broader functionality.

• Web Services: Develop web services to expose AS400 data and functionality to web-based applications, improving accessibility and integration with modern environments.

• Open Source Tools: Explore open-source tools that can complement traditional AS400 development processes, potentially streamlining development workflows.

The Future of AS400 Application Development

The AS400 remains a dependable platform for many organizations. As long as these systems are operational, there will be a demand for developers who understand the platform and can build, maintain, and modernize