What are the differences between DB2 UDB and DB2 OS/390?
Well, the two are comprised of completely different code bases. That means that the code is separate for the mainframe (z/OS and OS/390) DB2 and the distributed LUW (Linux, Unix, Windows) DB2.
Of course, IBM has done a reasonably good job of making DB2 on these different platforms compatible, at least from an interface perspective. With only a few differences SQL written for one platform will work on the other, though. There are, of course, differences in the setup and maintenance based on the type of platform. And the LUW DB2 has different optimization technology than the mainframe DB2.
And if you want to understand what is common to all of the SQL implementations across the different DB2 platforms, check out the SQL Reference for Cross Platform Development manual. It can be downloaded from the IBM Web site here.
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