AS400 Database Modernization
Many AS400 databases still rely on decades-old DDS-described physical and logical files. Converting them to modern SQL-defined DB2 for i tables and views unlocks standard tooling, better performance options, and easier integration, without requiring a database migration to a different platform.
DB2 for i has supported standard SQL for decades, but many AS400 databases were originally built using DDS (Data Description Specifications), IBM's older, non-SQL method of defining physical and logical files. Database modernization means converting those legacy structures to SQL-defined tables, views, and indexes, staying on the same integrated database while making it work more like a modern relational system.
DDS Files vs SQL Tables
DDS-described physical and logical files were the original way to define data structures on the AS400. They still work today, and DB2 for i continues to support them fully, but they lack some capabilities that SQL-defined tables and views provide natively, including certain modern indexing options, referential integrity enforcement defined at the database level, and easier integration with SQL-based reporting and analytics tools that expect standard relational metadata.
What Database Modernization Involves
A typical database modernization project converts DDS physical files to SQL tables and DDS logical files to SQL views and indexes, while preserving the record formats and field structures that existing RPG or COBOL programs depend on. Done correctly, this conversion is largely transparent to existing programs, since DB2 for i is designed to let SQL and native (record-level) access coexist against the same underlying data.
Why It Matters for Integration and Reporting
SQL-defined database objects are what most modern BI tools, reporting platforms, and integration middleware expect when connecting to a database. A database still described entirely in DDS terms can be harder for these tools to introspect and query efficiently. Database modernization is frequently a prerequisite step for effective API integration and analytics projects, rather than a standalone initiative.
Risks and Considerations
Database conversion projects carry real risk if approached carelessly: triggers, constraints, and journaling behavior tied to the original file definitions need to be carried forward correctly, and any program relying on undocumented DDS-specific behavior needs testing against the converted structures. Most successful database modernization projects convert incrementally, file group by file group, with thorough regression testing at each stage, rather than converting an entire database in one pass.