The AS/400 is a pretty successful platform, but still very little third party system software runs on it, or sells well if it does.

The lack of Oracle et al. on the AS/400 had a HUGE amount to do with the lack of a C compiler.

As for your claims about a “fully relational” database management system from Day 1 — which definition of “fully relational” are you using? While I’m aware of a number of such definitions (some of them with partisans who believe they have the One True Definitions, others favored by more tolerant people), off the top of my head I can’t think of any that makes your claim true.

Your comment about having to wait for a C compiler to port an RDBMS to the AS/400 is equally absurd; OS/400 had DB2 integrated and built-in since DAY ONE.

And your suggestion that the AS/400 database has some “wierdness” is also misleading. While it may not have always stayed in “lock step” with DB2 on other supported platforms, it has usually been the first DB2 to support many important features. Admittedly the System/38 and early AS/400 used a non-standard Data Definition Specifications (DDS) to define database tables, but support for SQL DDL has been available since the early ’90s (OS/400 V2 timeframe). In 1994 when V3R1 became available, IBM added support for referential integrity constraints and triggers.

DB2/400 UDB now supports more ANSI SQL DML and DDL standards than Oracle or Microsoft SQL Server (or any other commercially available DBMS), > 99% of the SQL standards, while Microsoft and Oracle support