The Complete Guide to AS400 Migration and Modernization

For more than three decades, AS400 (now known as IBM Power Systems), has quietly powered industries like banking, insurance, manufacturing, and healthcare. Payrolls, transactions, claims, production runs, all handled by a system built in the late 1980s that still runs today.

But here’s the catch: that reliability has become a liability in this era.

So, companies face an uncomfortable choice: keep patching a 30-year-old foundation, or migrate without risking data loss, compliance gaps, or business disruption.

That’s why AS400 migration and modernization is necessary. In this guide, we’ll walk through how enterprises can transition from AS400 legacy dependence to digital resilience.

What is AS400?

The AS400, launched by IBM in 1988 and now known as IBM Power Systems, was designed as an all-in-one business computing platform. It combined hardware, an integrated operating system, and a database that could run critical workloads with unmatched stability.

For decades, it powered core operations across industries. But what made AS400 revolutionary in the ’90s has turned into a roadblock in 2025 and beyond.

Why it’s a roadblock now:

• Aging technology and shrinking expertise: Most AS400 environments run on RPG, COBOL, or CL, and the number of skilled developers is rapidly declining
• Limited scalability: These systems weren’t built for cloud or distributed computing, making integration with modern analytics or APIs difficult
• Compliance and accessibility issues: Historical data often sits in formats that are hard to query or validate, complicating audits
• Rising operational cost: Hardware maintenance, licenses, and specialized support consume significant IT budgets with limited business return

What is the Solution Moving Ahead?

Enterprises managing legacy AS400 systems typically fall into one of two categories, that is – those ready to migrate and retire the system, and those who choose to modernize and continue it.

Two Common Use Cases for AS400 Systems

1. AS400 Migration and Decommissioning

When AS400 systems no longer support daily operations, enterprises migrate the data to modern databases or compliant archival platforms and then decommission the legacy system.

This approach:

• Eliminates recurring infrastructure and licensing costs
• Retains historical data for audits, analytics, or compliance
• Reduces dependency on legacy hardware and expertise

2. System Modernization

For organizations that still rely on AS400 for core operations, modernization means upgrading to the latest IBM Power Systems running IBM i. This preserves stability while introducing better performance, scalability, and integration with modern applications.

Modernization may include:

• Converting or refactoring RPG/COBOL applications
• Exposing data and workflows through APIs or web interfaces
• Integrating IBM i systems with analytics and cloud tools

Enterprises either migrate and retire from AS400 (decommission) or modernize and continue it (upgrade). Both require a strategy for managing decades of historical data cost-effectively and compliantly.

AS400 Migration Destinations: Where to Move Your Data

When you choose to migrate and decommission AS400, the historical data can be moved to one or a mix of the following destinations depending on compliance, performance, and budget goals.

1. Data Archiving Platform (Most common for decommissioning)

Purpose-built archival solutions that can store and secure legacy data for long-term access.

• Maintains audit readiness and data integrity (SOX, GDPR, HIPAA, DPDPA compliance)
• Enables retrieval of reports, transactions, or invoices after AS400 shutdown

Ideal when: You must retain data for 7–10+ years to ensure compliance and eliminate AS400 licensing and maintenance costs.

2. Cloud Storage or Cloud Databases

Migrates AS400 data to platforms like AWS RDS, Azure SQL, or Snowflake for analytics or modernization projects.

• Enables advanced reporting or AI/ML applications
• Requires transformation from DB2/400 formats to modern schemas

Ideal when: You want to use historical data for analytics, not just compliance.

3. Enterprise Data Warehouse (EDW)

Integrates AS400 datasets with enterprise warehouses such as Teradata, SAP BW, or Snowflake.

• Provides unified reporting across legacy and active systems

Ideal when: Your goal is to consolidate operational and legacy data for business intelligence.

4. Cold or Offline Storage

Exportsdata as PDFs, CSVs, or flat files into secure object storage like AWS S3 Glacier or Azure Blob.

• Least expensive but limited in searchability

Ideal when: You need infrequent retrieval and minimal user access.

A strategic guide to retire aging systems without risk. Learn how to reduce technical debt, control costs, and maintain compliance while keeping historical data accessible.

Download Now

Why do Enterprises Need to Migrate from AS400?

Let’s break down the core issues that make migration a necessity:

• Legacy Code and Shrinking Talent: Most AS400 applications run on RPG, COBOL, or CL programs. Developers who know these languages are retiring, leaving organizations dependent on an aging talent pool.
• Scalability and Integration: AS400 struggles to connect with modern analytics, cloud services, and APIs; and requires custom connectors or manual exports. Plus, data extraction for AI, reporting, or cross-platform workflows often require manual workarounds or middleware that slows innovation. This limits real-time data access and makes it difficult to leverage emerging technologies like AI and ML.
• Compliance and Data Retention: Many enterprises keep AS400 online solely for historical data access. But this data often sits in legacy formats that are hard to query or verify, hence, it creates risk under regulations.
• The Rising Cost of Staying Static: Maintaining on-premise AS400 environments along with the licensing, hardware, and support, consumes significant IT budgets. Every year spent on this adds to operational debt, which is both time and money. This ‘invisible tax’ limits agility, inflates costs, and prevents organizations from fully leveraging cloud capabilities like AI, automation, and advanced analytics.

Which Data must be migrated from the legacy AS/400?

At its core, AS400 migration means moving applications, data, and workloads from IBM’s legacy environment to modern cloud or hybrid platforms without breaking the business in the process.

Let’s start with the basics of what actually moves:

• Applications – Programs written in RPG, COBOL, or CL that contain the logic driving business processes like payroll, claims, or production planning
• Data – Structured records stored in DB2 for i databases and proprietary files that hold decades of operational history
• Workloads – The batch jobs, reports, and integrations that keep the business running every day

A successful migration preserves all three while improving scalability, security, and cost efficiency.

What are the Common Challenges in AS400 Migration?

Even with the best strategy, AS400 migrations are rarely smooth. The key is to anticipate the challenges early and design safeguards into the migration plan.

Let’s break down the most common challenges:

1. Complex Data Structures and Legacy Formats

AS400 data isn’t always stored in conventional relational tables. You’ll encounter DDS-defined files, logical files, and program-described data structures. On top of that, the system uses EBCDIC encoding and packed decimal (COMP-3) fields that don’t translate easily to modern databases. Without proper decoding and transformation, data corruption or loss can occur during extraction.

2. Application Dependencies and Compatibility Issues

AS400 applications are tightly coupled with business logic, data definitions, and interfaces existing within the same codebase. Many legacy applications also rely on fixed-format RPG or COBOL programs and hard-coded system integrations. One broken dependency can disrupt downstream workflows like billing, inventory, or reporting.

3. Downtime and Business Continuity Risks

Migrating large transactional workloads often requires temporary system shutdowns for extraction, testing, or validation. Prolonged downtime can impact operations, especially for industries that run 24/7 (banking, insurance).

4. Compliance and Data Retention Gaps

AS400 often stores sensitive financial or personal data. During migration, if retention rules, encryption, or access controls are not maintained, you risk violating SEC 17a-4, FINRA 4511, SOX, HIPAA, or GDPR. Loss of data lineage or auditability can trigger regulatory non-compliance and fines.

5. Resistance to Change

AS400 has a reputation for stability, “it’s been working for 30 years, why touch it?” That mindset creates inertia, especially in regulated industries. Cultural resistance delays decisions, stalls funding, and leads to half-finished modernization projects.

What are the best approaches to Migrate AS400 systems?

There’s no single path. Most enterprises adopt one (or a combination) of the following strategies depending on their risk appetite, budget, and modernization goals.

1. Rehosting

Moving AS400 workloads ‘as is’ from on-premise hardware to a cloud-hosted environments. It’s the fastest and least disruptive migration option, because it requires minimal code changes; teams can preserve existing IBM i applications and interfaces with little downtime.

However, since the architecture remains unchanged, this approach doesn’t unlock deeper modernization benefits like advanced analytics, API integrations, or AI capabilities until later stages.

When to use it:

• When you want to reduce data center costs quickly without changing application logic
• When business continuity and speed matter more than deep modernization

2. Re-platforming

Migrating data and applications to a modern environment while making selective optimizations. This approach typically moves the business logic to Linux or Windows-based platforms, and the data to cloud databases. It introduces scalability and integration with modern cloud tools while reducing dependence on IBM hardware and enables partial automation through ETL pipelines.

Although it does require code adjustments, testing, and data transformation, making it more complex than rehosting, it is still far less disruptive than complete re-architecture.

When to use it:

• When you want a balance between modernization and cost control
• When integration with cloud-native tools or analytics is a key goal

3. Re-architecting

Redesigning applications and data models entirely to align with modern architectures using microservices, containerization, and DevOps pipelines. Here, the AS400 business logic is rewritten in modern languages (Java, .NET, Python), and the data is restructured for scalability and advanced analytics.

This approach delivers true modernization, eliminating technical debt, and enabling seamless integration with AI, ML, and BI tools.

However, it comes with higher upfront investment and complexity, making it best suited for enterprises pursuing long-term digital transformation rather than short-term cost gains.

When to use it:

• When the goal is deep, future-ready modernization
• When legacy code or architecture limits innovation

4. Hybrid or Phased Modernization

Combining elements of all three approaches: rehosting some workloads for stability, re-platforming databases for analytics, and re-architecting select high-impact applications. It allows large enterprises to modernize at their own pace, aligning each phase with business priorities and minimizing disruption.

While this approach lowers migration risk and ensures continuous progress, it demands strong governance and coordination to prevent fragmented architectures across teams or regions.

When to use it:

• When you want to modernize gradually without major disruptions
• When different systems or business units require different approaches

How to Build an Effective AS400 Migration Plan

Migrating AS400 workloads to the cloud isn’t a one-time event but a multi-stage process that demands precision, planning, and strong governance.

Here’s a practical, step-by-step framework for building a successful

AS400 migration plan:

1. Assess the Current Landscape

Before you decide where to go, you need to understand what you have.

Key actions:

• Inventory applications and workloads: Identify what’s running on AS400 — ERP modules, batch jobs, integrations, and reporting tools
• Map dependencies: Understand how applications interact with external systems (e.g., CRMs, supply chain tools)
• Analyze data volumes and structures: Determine which datasets are active, which are historical, and which can be archived
• Identify compliance and retention requirements: Some data must stay accessible for years depending on regulations

2. Define Migration Goals and Strategy

Not all migrations are equal; hence, your approach should align with your long-term IT roadmap.

Key actions:

• Clarify intent: Is your goal to reduce infrastructure costs (lift-and-shift) or enable full digital modernization (re-platform or re-architect)?
• Choose the right migration approach:
• Rehost (Lift-and-Shift) – move workloads ‘as is’ for speed
• Re-platform – modernize partially for flexibility
• Re-architect – rebuild for long-term scalability
• Establish success metrics: Define KPIs such as reduced maintenance cost, improved uptime, faster reporting, or compliance readiness
• Build a project timeline: Include buffer time for validation and parallel runs

3. Prepare Data for Migration

This is often the most complex and overlooked step, especially for legacy AS400 systems.

Key actions:

• Extract and cleanse data: Use ETL tools to decode EBCDIC, packed decimals, and other IBM-specific formats
• Transform and validate: Standardize schemas and verify data integrity through record counts and hash totals
• Plan for data archival: Historical or inactive data should move to a compliance-grade archive (like Archon Data Store™)
• Ensure compliance mapping: Tag sensitive or regulated data to enforce retention and access controls post-migration

4. Execute the Migration

This is where planning meets action. Each migration should follow a controlled, iterative rollout to reduce disruption.

Key actions:

• Migrate workloads in phases: Start with non-critical systems, then expand to core applications
• Maintain parallel runs: Keep AS400 live alongside the new system until validations are complete
• Test extensively: Validate application functionality, performance, and data integrity after each migration phase
• Ensure rollback mechanisms: Always have a contingency plan in case of errors or downtime

5. Optimize and Govern Post-Migration

Migration success isn’t measured on go-live day; it’s measured by stability and long-term efficiency.

Key actions:

• Monitor performance and cost: Track resource utilization and spending
• Implement governance: Define policies for data access, backups, and lifecycle management
• Decommission safely: Once validation is complete, decommission AS400 infrastructure to cut costs
• Continuously modernize: Incrementally refactor or re-architect migrated workloads for cloud-native performance over time

Once workloads and historical data are successfully migrated to modern or archival systems, the legacy AS400 environment must be decommissioned. This final step closes the loop; freeing organizations from hardware and maintenance costs while ensuring that all historical information remains accessible and compliant.

How to Decommission AS400 Safely?

Migrating workloads to the cloud is only half the job. Once data and applications are live in the new environment, the real question begins: What happens to the historical data that is left behind on AS400 and is still needed for audits?

Those historical records like customer data, transactions, audit logs, and reports are not disposable. In most industries, they’re subject to strict retention and regulatory obligations. Deleting them risks legal exposure; keeping them on legacy infrastructure drains budgets.

The only sustainable answer is archival, and decommissioning done right.

Key steps for a safe shutdown:

1. Dependency verification: Confirm that no live applications, integrations, or scheduled jobs still reference the AS400 environment
2. Validation checks: Cross-verify record counts and reconcile reports between source and archive
3. Stakeholder sign-off: Compliance, IT, and business owners must approve archival integrity before power-down
4. Secure retirement: Erase or destroy residual media using certified data-wiping processes
5. License and cost optimization: Cancel hardware maintenance, software licenses, and support contracts tied to AS400

When done right, archival and decommissioning don’t just close a chapter; they unlock new possibilities. This is where modernization truly begins — when historical data stops being a liability and becomes an asset.

AS400 Modernization within IBM Power Systems

Not every organization plans to retire from AS400 entirely. Many choose to modernize within the IBM ecosystem, upgrading to the latest IBM Power Systems running IBM i to improve performance, scalability, and support while retaining the reliability that AS400 is known for.

Upgrading to IBM Power Systems with IBM i typically includes:

• Hardware modernization: Moving from older AS400 machines to new Power Systems with enhanced compute and storage performance
• OS and database updates: Upgrading IBM i and DB2 versions to support modern interfaces, APIs, and integration layers
• Application optimization: Refactoring or wrapping existing RPG/COBOL applications with modern APIs or web interfaces for better usability and interoperability
• Process automation: Leveraging IBM i modernization tools to integrate with DevOps pipelines, analytics, or AI workloads

Why Archiving Historical Data Separately Matters

A common mistake during modernization is migrating all legacy data into the upgraded IBM environment. Doing so increases storage and maintenance costs without real operational benefit.

Instead, enterprises can archive historical AS400 data in a secure, compliant archival platform, separate from the upgraded production systems.

This approach provides the best of both worlds:

• Frees expensive Power Systems resources from decades of inactive data
• Archived data remains immutable, searchable, and audit-ready
• The upgraded IBM i environment runs faster and cleaner with only active workloads
• Retention and access controls can be managed independently of production systems

How Archon™ Helps Overcome the Challenges of AS400 Migration and Decommissioning

Migrating AS400 workloads is only half the battle; making the data usable, compliant, and accessible after migration is where real modernization begins. This is where Archon™ comes in. Instead of treating migration, archival, and decommissioning as separate efforts, Archon™ acts as the orchestration layer that ties everything together from extraction to compliance to post-migration analytics.

Here’s how each Archon™ module fits into the AS400 modernization journey.

1. Archon Analyzer™– Discover, Analyze, and Decide

Before any data moves, enterprises need a clear picture of what exists inside their AS400. That’s where Archon Analyzer™ begins the process. It connects directly to AS400 systems to perform comprehensive migration analysis, helping to know what’s worth migrating, what can be archived, and what can be safely decommissioned.

What it does:

• Migration Analysis: Scans and profiles AS400 databases to assess data volumes, complexity, and readiness for migration
• Legacy Application Analysis: Identifies and categorizes old RPG/COBOL applications which ones to migrate, retire, or rewrite
• Application Code Analysis: Maps dependencies across code, data, and jobs, revealing hidden coupling that could break during migration
• Relationship Modelling: Builds a visual map of how programs, data files, and business processes interconnect

2. Archon ETL™– Act with Intelligent Automation

Once the roadmap is clear, Archon ETL™ takes over to handle the actual data movement securely and intelligently. It’s a Smart ETL™ framework built to handle the unique challenges of AS400. Whether it’s a batch run, live streaming, or change data capture (CDC), it keeps the migration consistent and verifiable across environments.

How it helps:

• Connectors: Directly integrates with AS400 databases, on-prem systems, and cloud targets like AWS or Azure
• Smart ETL™: Automates data extraction, transformation, and loading while maintaining schema integrity
• Migration Automation: Handles EBCDIC-to-ASCII conversion, data cleansing, and dependency-based sequencing
• Program Management: Provides progress tracking, error handling, and version control for migration workflows
• Validation: Applies validation rules like record counts, hash totals, and integrity checks to ensure every byte matches the source
• Data Mapping: Performs schema discovery and mapping, translating AS400’s proprietary structures into modern relational or cloud-ready formats (SQL, Parquet, JSON).

3. Archon Data Store™– Manage, Govern, and Retain

After migration, the challenge shifts from moving data to governing and preserving it, especially for regulatory or audit requirements. Archon Data Store™ (ADS) is where AS400 data lands for long-term management and compliance.

What it does:

• AI-enriched indexing: Metadata tagging and intelligent discovery make archived AS400 data instantly searchable for compliance teams, auditors, or analysts
• Storage Tiering: Automatically shifts inactive data to low-cost storage (on-prem or cloud) to optimize costs by 60-80%
• Data Governance: Enforces retention, immutability, legal holds, and audit trails in line with SOX, HIPAA, and GDPR
• Secure and Compliant: Supports encryption, WORM storage, and role-based access controls
• Unified storage: Consolidates structured and unstructured data into a single, searchable repository
• Role-based access controls: Ensures only authorized users can query or export data, with full audit visibility
• Universal Compatibility: Runs everywhere on-prem, hybrid, or cloud with connectors to AWS, Azure, and other ecosystems

Together, these three modules, Archon ETL™, Archon Data Store™, and Archon Analyzer™, eliminates fragmented tools and one-off scripts. It ensures data integrity, compliance, and accessibility allowing enterprises to decommission AS400 confidently.

What are the Tangible and Technical Benefits with Archon Data Store™

• Lower costs: Retiring AS400 and moving inactive data to ADS cuts infrastructure, licensing, and support expenses
• Zero compliance risk: Immutable storage, retention controls, and full audit trails keep every record defensible under SOX, HIPAA, and GDPR
• Smarter access: Archived data remains instantly searchable for audits, analytics, or investigations; no need to keep AS400 live
• Streamlined operations: Active systems run faster with only current workloads, while ADS handles long-term governance and retention
• Faster ROI: Clean data, automation, and built-in governance shorten modernization timelines and accelerate digital transformation

AS400 served enterprises well for decades, but what once symbolized reliability has now become a barrier to agility. With the right strategy and the right tools, you can decommission AS400 confidently without losing a single byte of data or integrity.

Explore how Archon™ fits your modernization roadmap. Talk to our team about building your AS400 exit plan. 👉 Book a Demo