LANSA IBM i Modernization: Scaling Web UI from Legacy RPG Code

The IBM i (AS/400) remains the most resilient platform in enterprise history, yet for many organizations, it has become a gilded cage. While the core RPG logic is bulletproof, the user interface and the speed of delivery are not. Most enterprises attempting lansa modernization scaling from legacy RPG code find themselves trapped in a cycle of proprietary toolsets that trade one form of technical debt for another.

According to Replay's analysis, 70% of legacy rewrites fail or significantly exceed their timelines because they attempt to manually document and reconstruct decades of undocumented business logic. When you are dealing with a $3.6 trillion global technical debt crisis, the traditional "rip and replace" or "proprietary refactor" models are no longer viable.

TL;DR: Traditional IBM i modernization via LANSA often results in proprietary lock-in and slow scaling. Replay offers a "Visual Reverse Engineering" alternative that converts video recordings of legacy workflows into documented React code and Design Systems. This reduces the average time per screen from 40 hours to just 4 hours, allowing enterprises to modernize in weeks rather than the typical 18-24 month timeline.

The Hidden Friction in LANSA Modernization Scaling From RPG#

For decades, LANSA has been a go-to for IBM i shops. It provides a low-code environment that bridges the gap between the "Green Screen" (5250) and the web. However, the friction begins when you attempt to scale. The "lansa modernization scaling from" legacy RPG code often hits a wall because the output is still tied to a proprietary runtime.

Industry experts recommend moving toward open standards like React and TypeScript to ensure long-term maintainability. The problem is that 67% of legacy systems lack any form of documentation. Developers are forced to "archeology" through thousands of lines of RPG and DDS (Data Description Specifications) just to understand how a single subfile grid is supposed to behave.

Video-to-code is the process of capturing real-time user interactions with a legacy system and using AI-driven visual analysis to generate clean, documented frontend components and architectural flows.

By using Replay, architects can bypass the manual discovery phase. Instead of writing LANSA-specific scripts, you record the legacy application in action. Replay’s AI Automation Suite identifies the patterns, the data bindings, and the UI components, outputting a modern React-based Design System.

Why Manual Rewrites and Refactors Fail#

The 18-month average enterprise rewrite timeline is a conservative estimate. In the world of Financial Services and Insurance, these projects frequently stretch into year three or four. The issue isn't the talent; it's the methodology.

The Cost of Discovery#

Manual modernization requires a developer to:

1. •Read the RPG/CL source code.
2. •Map the DDS to a modern layout.
3. •Manually recreate the business logic in a new language.
4. •Test for parity.

This process takes roughly 40 hours per screen. With lansa modernization scaling from existing codebases, you are still tethered to the original logic's limitations. Replay reduces this to 4 hours per screen by automating the discovery and code generation phases.

Comparison: LANSA vs. Replay vs. Manual Rewrite#

Replay vs. LANSA Modernization Scaling From Legacy Architectures#

When you look at lansa modernization scaling from a strategic perspective, the goal is usually to provide a better UX for employees or customers. LANSA achieves this by wrapping the legacy code. Replay achieves this by extracting the intent.

Replay's Library feature allows you to build a comprehensive Design System based on the actual usage patterns of your IBM i applications. Instead of guessing how a "Customer Search" should look in React, Replay sees how it looks in the Green Screen and generates a themed, accessible component.

Example: Converting an RPG Subfile to a React Data Grid#

In a traditional IBM i environment, a subfile (SFL) might look like this in DDS:

text
A          R SFLRCD                    SFL
A            FLD01          5A  B  4  2
A            FLD02         20A  O  4  8
A            FLD03         10Y 0O  4 30

To modernize this manually, you would need to write a significant amount of boilerplate. Replay’s engine identifies this pattern from a video recording and generates a high-quality React component using TypeScript.

typescript
// Generated by Replay AI Automation Suite
import React from 'react';
import { DataGrid, GridColDef } from '@mui/x-data-grid';
import { useLegacyData } from '../hooks/useLegacyData';

interface CustomerSubfileProps {
  batchId: string;
}

export const CustomerSubfile: React.FC<CustomerSubfileProps> = ({ batchId }) => {
  const { data, loading } = useLegacyData(batchId);

  const columns: GridColDef[] = [
    { field: 'id', headerName: 'ID', width: 90 },
    { field: 'customerName', headerName: 'Customer Name', width: 200 },
    { field: 'balance', headerName: 'Current Balance', type: 'number', width: 150 },
  ];

  return (
    <div style={{ height: 400, width: '100%' }}>
      <DataGrid 
        rows={data} 
        columns={columns} 
        loading={loading}
        pageSize={10}
        aria-label="Legacy Customer Subfile Modernized"
      />
    </div>
  );
};

This component isn't just a "skin." It is a functional, documented piece of a larger Flow that understands the state transitions of the original application.

Scaling the Modernization Factory#

The challenge with lansa modernization scaling from RPG is the "talent gap." Finding developers who understand both 1980s RPG III and 2024 React is nearly impossible. Replay bridges this gap by allowing your modern frontend teams to work with the output of the legacy system without needing to touch the underlying AS/400 code.

Step 1: Record Workflows#

Your subject matter experts (SMEs) record themselves performing standard tasks—ordering parts, processing insurance claims, or updating patient records. These recordings serve as the "source of truth."

Step 2: Visual Reverse Engineering#

Replay’s AI analyzes the video. It identifies input fields, buttons, navigation patterns, and data tables. It maps out the "Blueprints" of the application.

Step 3: Component Generation#

The system generates a Design System that matches your corporate branding. Every screen recorded is converted into a React component that is ready for integration.

Step 4: Logic Integration#

While Replay handles the UI and the "Flows" (the frontend architecture), your backend team can focus on exposing the RPG logic as REST or gRPC APIs. Because the UI is already built and documented, the integration phase is 50% faster.

Security and Compliance in Regulated Industries#

For industries like Healthcare, Government, and Manufacturing, "Cloud-only" is often a dealbreaker. Replay is built for these environments. With SOC2 compliance, HIPAA-readiness, and the option for On-Premise deployment, it satisfies the strict requirements that often stall lansa modernization scaling from legacy environments.

According to Replay's analysis, the biggest risk in modernization isn't the technology—it's the data loss and the "logic drift" that occurs when developers try to guess how old code works. By using Visual Reverse Engineering, you ensure that the new system performs exactly like the old one, because it was built from the actual user experience.

The Financial Reality of Technical Debt#

The $3.6 trillion technical debt isn't just a number; it's a drag on innovation. Every dollar spent maintaining a LANSA runtime or a legacy RPG stack is a dollar not spent on AI, customer experience, or market expansion.

When evaluating lansa modernization scaling from your current state, consider the opportunity cost. If a manual rewrite takes 24 months, what is the cost of being "stuck" for those two years?

Replay allows you to move at the speed of the market. By automating the most tedious 70% of the modernization process—documentation, UI recreation, and workflow mapping—you free your team to focus on the high-value logic that actually differentiates your business.

Implementing a Modernization Blueprint#

To successfully scale, you need more than just a tool; you need a blueprint. Replay provides a structured environment where architects can manage the transition.

1. •The Library: A centralized repository of all your modernized components.
2. •The Flows: A visual map of how users move through your application, ensuring no edge cases are missed during the transition from IBM i.
3. •The Blueprints: An editor that allows you to refine the AI-generated code before it enters your production codebase.

typescript
// Example of a Replay Blueprint for a modern Insurance Claim Flow
export type ClaimWorkflow = {
  step: 'Capture' | 'Validate' | 'Submit';
  legacyScreenId: string;
  modernComponent: React.ReactNode;
};

const insuranceFlow: ClaimWorkflow[] = [
  {
    step: 'Capture',
    legacyScreenId: 'SCR001_CLAIM_ENTRY',
    modernComponent: <ClaimEntryForm />,
  },
  {
    step: 'Validate',
    legacyScreenId: 'SCR005_ERROR_CHECK',
    modernComponent: <ValidationDashboard />,
  }
];

By defining these flows, you ensure that lansa modernization scaling from legacy systems remains consistent across the entire enterprise.

Frequently Asked Questions#

How does Replay handle complex RPG business logic?#

Replay focuses on the Visual Reverse Engineering of the user interface and application flows. It documents the behavior and state transitions of the legacy application. While it doesn't "rewrite" the RPG backend code, it provides the frontend and documentation necessary for your developers to connect the modern UI to existing or refactored APIs with 100% clarity on the required inputs and outputs.

What is the difference between screen scraping and Visual Reverse Engineering?#

Screen scraping (like some older LANSA or terminal emulation tools) simply "skins" the existing 5250 stream in real-time. It is fragile and depends on the legacy system remaining unchanged. Visual Reverse Engineering by Replay captures the intent and structure of the UI from video, then generates independent, modern React code. This code is not "connected" to the old screen; it is a brand-new, clean-code implementation that stands on its own.

Can Replay integrate with existing LANSA-based web apps?#

Yes. If you have already started lansa modernization scaling from RPG and have a web-based LANSA interface, Replay can record those web workflows just as easily as Green Screens. This allows you to migrate from the proprietary LANSA framework to a standard React/TypeScript stack without losing the work you've already put into your web UI.

Is Replay secure for use in Financial Services or Healthcare?#

Absolutely. Replay is designed for regulated industries. We offer SOC2 and HIPAA-ready environments, and for organizations with strict data sovereignty requirements, we provide On-Premise deployment options. This ensures that your sensitive application flows and business logic never leave your secure perimeter.

How does Replay achieve a 70% time saving?#

The majority of modernization time is spent on discovery, manual documentation, and UI development. Replay automates these three pillars. By converting video recordings directly into documented React components and architectural flows, we eliminate the "archeology" phase of modernization. What typically takes 40 hours of manual labor per screen is reduced to 4 hours of AI-assisted generation and refinement.

Ready to modernize without rewriting? Book a pilot with Replay