iCan Blog Archive

Last year, I wrote a blog about AnyNet support (actually, the lack of it) in the 7.1 release. But what about SNA applications? If you are still using some old SNA applications, should you be concerned they won’t work at some point?

SNA (Systems Network Architecture) has been a part of the operating system since the S/38 days and continues to be there, although over time certain features and functions have gone away. In general, when you see functions that no longer work, it’s due to external hardware dependencies that don’t have replacements from IBM.

For “native” SNA support in OS/400, i5/OS and IBM i, low-level support of the SNA architecture was part of the I/O Processors (IOPs) that were attached to the system. In particular, the “DLC” (Data Link Control) layer of the SNA protocol was implemented in the IOPs. With the more recent hardware, IBM has moved away from supporting IOPs and is just using I/O Adapters (IOAs). With this change, the DLC layer of software that SNA was dependent upon was no longer available. Rather than re-implement the DLC layer in the operating system, IBM chose to use other technologies to support the SNA applications – AnyNet and then Enterprise Extenders; these allowed applications based upon the SNA protocol stack to run over TCP/IP networks.

Also in the past, there were many different flavors of link-level protocols – Token Ring, Ethernet, ISDN, ATM, Frame Relay. X.25, etc. Most of those protocols have also disappeared over the years and today, Ethernet is primarily what everyone uses to connect their systems to their networks.

In the IBM i 7.4 release, IBM has removed old, unsupported networking interfaces from the operating system. This is documented in Chapter 4 in the 7.4 Memo to Users.

It’s safe to say that in the future SNA-based applications will continue to be supported. SNA-based applications include things like SNADs, Display Station Passthrough, DDM, ICF applications, etc.

IBM i documentation on SNA is all still available. In the Knowledge Center, you’ll find it under Networking->Network Communications. The documentation that was never incorporated into the Knowledge Center is also still available and references to it can be found in the “Related Information” section.

This blog post was edited for currency on February 5, 2020.

This blog post was originally published on IBMSystemsMag.com and is reproduced here by permission of IBM Systems Media.