For decades, IBM AS/400, iSeries, and today’s IBM i platforms have supported critical business applications across manufacturing, distribution, retail, finance, healthcare, and other industries. At the heart of many of these environments is Db2 for i, a reliable database tightly integrated with IBM i applications.
However, changing business requirements, modern application architectures, cloud adoption, and the growing demand for open database technologies are encouraging organizations to evaluate alternatives. One option is migrating data and applications from Db2 for i on AS/400 or iSeries to EnterpriseDB (EDB), a PostgreSQL-based database platform designed for enterprise workloads.
A well-planned migration can become an important part of IBM i modernization, helping organizations reduce platform dependencies, support modern applications, and build a more flexible data architecture.
Why Consider Migrating Db2 for i to EnterpriseDB?
Db2 for i provides deep integration with IBM i and is well suited to traditional RPG, COBOL, and other IBM i workloads. But organizations may encounter challenges when they want to connect legacy applications with modern development frameworks, cloud platforms, APIs, analytics tools, and distributed architectures.
EnterpriseDB provides an enterprise-focused PostgreSQL environment that can support modern applications and development practices.
Common reasons for considering an AS400 migration to EnterpriseDB include:
• Modernizing legacy database environments
• Supporting cloud-native application architectures
• Expanding the use of open-source technologies
• Integrating data with modern applications and APIs
• Supporting developers familiar with PostgreSQL
• Reducing dependency on proprietary database technologies
• Preparing legacy workloads for broader digital transformation
The objective should not simply be to move database tables from one platform to another. Instead, the migration should be treated as part of a broader modernization strategy.
Understanding the AS400, iSeries, and IBM i Database Environment
AS/400 is the historical name associated with IBM's midrange platform. Over time, the platform evolved through names including iSeries and System i and eventually became IBM i on IBM Power Systems.
Many organizations still use terms such as AS400 database, iSeries database, or AS400 DB2 when describing their environments. Technically, modern IBM i systems use Db2 for i, which is deeply integrated with the operating system.
This integration is one of the biggest considerations during migration.
Db2 for i does not operate in isolation. Business applications may depend on:
• RPG and COBOL programs
• CL programs
• Stored procedures
• Triggers
• Views
• Physical and logical files
• Journaling
• Data queues
• Batch jobs
• Embedded SQL
• IBM i security and object authorities
Therefore, migrating the database requires a detailed assessment of application dependencies before any production data is moved.
Key Challenges in Migrating Db2 for i to EnterpriseDB
An AS400 migration from Db2 for i to EnterpriseDB requires more than converting database schemas. Differences between the platforms can affect applications, SQL statements, data types, security, and database behavior.
1. Database Schema Conversion
Db2 for i and PostgreSQL/EnterpriseDB use different database structures and conventions.
Tables, indexes, constraints, views, sequences, stored procedures, and other database objects must be assessed and mapped to their EnterpriseDB equivalents.
A schema-conversion assessment should identify:
• Tables and columns
• Primary and foreign keys
• Indexes
• Views
• Triggers
• Stored procedures
• User-defined functions
• Constraints
• Sequences
• Database relationships
Automated conversion tools can accelerate this process, but complex environments usually require manual validation.
2. Data Type Compatibility
Data types are another important consideration.
Db2 for i applications may use packed decimal, zoned decimal, character, date, timestamp, binary, and other data types that need appropriate PostgreSQL-compatible mappings.
Special attention should be given to:
• Numeric precision and scale
• Date and timestamp handling
• Character encoding
• Nullability
• Large objects
• Decimal calculations
• Legacy data formats
Incorrect data-type mapping can create application errors or unexpected results after migration.
3. SQL and Application Compatibility
Existing RPG, COBOL, or other applications may contain embedded SQL designed specifically around Db2 for i behavior.
SQL statements need to be reviewed for compatibility with EnterpriseDB/PostgreSQL.
This may include changes to:
• SQL syntax
• Functions
• Joins
• Date operations
• String functions
• Identity/sequence handling
• Stored procedures
• Transaction behavior
If applications are also being modernized, this migration can provide an opportunity to replace tightly coupled database logic with APIs and modern application services.
A Step-by-Step AS400 Migration Approach
A structured migration methodology can reduce risk and improve the chances of a successful transition.
Step 1: Assess the Existing IBM i Environment
Start by creating an inventory of databases, tables, applications, programs, interfaces, jobs, and dependencies.
Identify which workloads must remain on IBM i and which can move to EnterpriseDB.
Step 2: Analyze Database Dependencies
Map relationships between Db2 for i objects and the applications that use them.
This dependency analysis helps determine migration complexity and identifies applications that could be affected by database changes.
Step 3: Design the EnterpriseDB Architecture
Define the target EnterpriseDB environment based on application requirements.
Consider:
• On-premises versus cloud deployment
• High availability
• Backup and recovery
• Security
• Performance
• Monitoring
• Disaster recovery
• Network connectivity
Step 4: Convert the Database Schema
Create the EnterpriseDB schema and map Db2 for i objects to their PostgreSQL-compatible equivalents.
Validate constraints, indexes, relationships, and data types before transferring production data.
Step 5: Migrate and Validate Data
Move data using an appropriate migration strategy. Depending on the workload, organizations may choose an offline migration, staged migration, or a replication-based approach to minimize downtime.
After migration, validate record counts, data types, relationships, and critical business calculations.
Step 6: Modernize Applications
Database migration and IBM i modernization can be performed together.
Applications can be refactored or rewritten using modern technologies while EnterpriseDB becomes the database layer for new applications.
Organizations can also expose existing IBM i functionality through APIs and gradually transition workloads rather than replacing everything at once.
Step 7: Test and Cut Over
Perform functional, integration, performance, security, and user-acceptance testing.
Once the EnterpriseDB environment meets business requirements, establish a cutover plan with rollback procedures and monitoring.
How IBM i Modernization Fits Into the Migration
A database migration should ideally be part of a larger IBM i modernization roadmap.
Instead of treating modernization as a single large replacement project, organizations can take an incremental approach.
For example:
Assessment → Database modernization → API enablement → Application modernization → Cloud adoption
This approach allows businesses to modernize critical components while continuing to operate existing IBM i applications.
In some cases, organizations may also choose a hybrid architecture in which IBM i remains responsible for selected workloads while EnterpriseDB supports modern applications and services.
Benefits of Migrating to EnterpriseDB
A successful migration can provide several strategic benefits:
Modern Application Development
EnterpriseDB provides a PostgreSQL-based environment that can integrate with modern programming languages, frameworks, APIs, analytics platforms, and cloud services.
Greater Architectural Flexibility
Moving selected workloads away from tightly coupled IBM i database dependencies can give organizations greater flexibility when designing new applications.
Easier Integration
EnterpriseDB can serve as a data platform for applications that need to interact with modern APIs, microservices, reporting systems, and other enterprise platforms.
Support for Digital Transformation
An AS400 migration can become a foundation for broader modernization initiatives, including cloud migration, application transformation, data analytics, and AI initiatives.
Final Thoughts
Migrating Db2 for i from an AS/400 or iSeries environment to EnterpriseDB is a significant technology transformation. The database itself is only one part of the equation. Application dependencies, SQL compatibility, data types, integrations, security, performance, and business processes must all be considered.
For organizations pursuing IBM i modernization, the migration can provide an opportunity to move beyond legacy database dependencies while creating a foundation for modern applications and cloud-based architectures.
The best approach is usually incremental: assess the current IBM i environment, understand dependencies, design the EnterpriseDB target architecture, migrate and validate data, modernize applications where appropriate, and transition workloads in controlled phases.
With careful planning and technical expertise, businesses can turn an AS400 migration from a database replacement project into a broader modernization strategy that supports their long-term technology roadmap.
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