IBM.Data.DB2

Defender IBM (or more accurately, allows its clients to protect) their mainframe access to DB2 is very close. I suspect this is because even business supporting applications even try to connect (JDBC clients that don't have the license file they need don't even get their requests appearing on the TCP mainframe ports, they are blocked on the client side) - mainframe is usually business critical as most desktop and server applications only dream of becoming :-).

When using JDBC drivers, one type 4 driver is used to access all DB2 platforms (LUW, iSeries, System z, etc.), but in fact you must have a license file installed in your CLASSPATH for certain platforms, or you get an exception.

This license file is of the form " db2jcc_cisuz.jar

", where cisuz specifies which platforms are allowed to access (cu is the most common, but does not give access to iSeries or System z).

Typically you need to purchase DB2 Connect from IBM in order to obtain these files, and I suspect this will be a similar situation for the .NET platform. You may find that the DB2 Connect products have .NET client drivers as well as JDBC (I haven't looked). Look for the "Enterprise" version of this product, as the standard ones are unlikely to be System z licensed.

And just a minor annoyance, it's not OS / 390 (unless you're one of the rare Japanese customers who pay specifically to support this dinosaur). This is z / OS.