> Although I had listed the versions of IBM's 40-year-old database running on Linux or Unix or Windows (LUW) and its System Z mainframe, I neglected to mention the version running on the mid-range server once known as AS/400, now – after several intermediary name changes – called iSeries or IBM i.
Actually between this article and the previous article to which he refers - he doesn’t link to it but it is [0] - he’s still missing a DB2 variant, albeit arguably the least used, most obscure, and least supported (as in, still under support, but largely in maintenance mode) - DB2 Server for VSE and VM, [1] possibly better known under its original name of SQL/DS. It is actually IBM’s oldest official relational database product, it shipped first for VM/CMS, and then DB2 for MVS came out second. (There were earlier IBM relational databases that were research projects only, or provided to customers outside of IBM’s normal software support, but SQL/DS was the first to ship as a fully supported IBM software product.)
Originally, DB2 was just the name for the MVS relational database. The VM/CMS relational database was SQL/DS (later ported to DOS/VSE as well), and the OS/2 relational database was OS/2 Extended Edition Database Manager. And then IBM decided to adopt “DB2” as an overarching brand for all three, as well as for the relational database layer of the AS/400’s OS/400 operating system (DB2/400, now DB2 for IBM i). But they are actually four different code bases - the OS/2 database evolved into the current Linux/Unix/Windows DB2 - with incompatible feature sets, and independent (not in synch with each other) version numbering
[0] https://www.theregister.com/2024/06/27/ibm_ai_optimization_d...
[1] https://www.ibm.com/mysupport/s/topic/0TO0z0000006v3rGAA/db2...