DRDA and Distributed Database Concepts

Learning Objective

By the end of this lesson, you will be able to explain what DRDA is and why it matters for querying data across more than one Db2 for i system.

Simple Explanation

Every query covered so far in this course has run against a single Db2 for i system. DRDA (Distributed Relational Database Architecture) is IBM's standard for letting a program on one system query or update a Db2 for i database on a different system, using ordinary SQL, as if that remote database were reachable directly.

SELECT CUSTNBR, CUSTNAME
FROM WAREHOUSE_SYS.MYLIB.CUSTMAST;

Here, WAREHOUSE_SYS represents a connection to a different remote IBM i system, set up ahead of time, so the same familiar SELECT syntax can reach a table that physically lives elsewhere.

Why It Matters

This connects directly to the integration thinking already covered in the Modern IBM i / APIs / Integration lessons: sometimes the "other system" a program needs to reach is another Db2 for i database, not a REST API. DRDA is the SQL-native way of reaching that other database, distinct from the REST/JSON approach covered for reaching non-database systems, or for systems that are not IBM i at all.

Practical Example

Imagine a company with a central IBM i system holding customer data, and a separate regional IBM i system that needs to check a customer number against the central system before completing a local order. Rather than building a REST API for this internal, database-to-database need, as covered in the Integration lessons, DRDA lets the regional system's SQL directly query the central system's CUSTMAST table, using the same SQL already familiar from earlier in this course.

This is a simplified, illustrative example rather than a specific real architecture, but it reflects a genuinely common reason DRDA is used.

Common Confusions

"Is DRDA the same thing as the REST API integration covered earlier in this course?" No. Both let one system reach data or logic on another system, but DRDA is specifically for database-to-database SQL access between Db2 systems, while the REST API lessons covered a more general, system-agnostic way of exposing or calling logic over HTTP.

"Does DRDA require rewriting queries in a special distributed SQL dialect?" No. Once the connection to the remote system is set up, ordinary SQL, like the SELECT above, works against the remote table largely the same way it would against a local one.

"Is DRDA only useful between two IBM i systems?" DRDA is IBM i's own established, cross-system distributed database standard; while this lesson focuses on the IBM i-to-IBM i case as the clearest example, the underlying idea, standardized SQL access to a remote relational database, is the important conceptual takeaway.

Quick Recap

• DRDA lets a program query or update a Db2 for i database on a different system using ordinary SQL.
• It is the SQL-native, database-to-database counterpart to the REST/JSON integration approach covered earlier in this course.
• Once a connection to the remote system exists, familiar SQL syntax works against the remote table largely as it would locally.
• DRDA is best suited to genuine database-to-database needs, distinct from reaching a non-database or non-IBM i system.

Try Asking the AI Tutor

Use the AI Tutor to ask follow-up questions about this lesson. For example, try asking:

• "How would I decide between DRDA and a REST API approach for a specific integration need between two systems?"
• "What would a program need to have set up before it could query a remote system's table using DRDA?"