Concept Clarification of IBM DB2, AS400, Mainframe, etc.

There are many technical names related to DB2, AS400 etc from IBM. These are confusing. Here are some clarification.

DB2 is a relational model database server developed by IBM. The name confusion mainly comes from the various platforms that DB2 runs on. On different platforms, DB2 is different. It has different features and may be even written in different languages. To differentiate products on different platforms, a formal name IBM uses is "product FOR platform". For example, DB2 for OS/390, DB2 for z/OS, DB2 for i.

AS/400 is a system that includes both an operating system (OS/400), DB2, and others.
AS/400 is now called IBM System i (iSeries ), or more recently IBM power system. And its operating system OS/400 is now called IBM i operating system.

z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It is the successor to OS/390, which in turn followed a string of MVS versions.

AS/400 is not a mainframe system. The IBM System i is a midrange computer system for i users. In 2008, IBM announced its integration with the System p platform. The unified product line is called IBM Power Systems and features support for the IBM i (previously known as i5/OS or OS/400), AIX and Linux operating systems.

DB2 UDB stands for DB2 Universal Database. It used to mean DB2 for the Linux-unix-Windows version. Now it can also mean DB2 on mainframe.

At this point, the mainframe version of DB2 UDB and the server version of DB2 UDB were coded in entirely different languages(PL/S for the mainframe and C++ for the server).

DB2 UDB Version 8 for z/OS now requires a 64-bit system.

In 2006, IBM announced "Viper": DB2 9 on both distributed platforms and z/OS.
In 2009, IBM announced "Cobra": DB2 9.7 for LUW(Linux, Unix, Windows).
In 2009, IBM announced DB2 pureScale. It is a database cluster soluction for non-mainframe platforms.
In 2010, IBM announced that DB2 10 for z/OS would enter beta testing.

DB2 for i(the former DB2/400) is very closely incorporated into the operating system of the IBM System i machines.

Reference

[1] http://en.wikipedia.org/wiki/IBM_DB2
[2] http://en.wikipedia.org/wiki/Z/OS
[3]http://search400.techtarget.com/expert/KnowledgebaseAnswer/0,289625,sid3_cid414164,00.html