SNA is an IBM Networking Architecture used by Mainframes and Midranges for Data Exchange. It is a deterministic architecture. It uses a hierarchical method of definitions and leaves very little to chance. Bandwidth, connections, and users all need to be predefined.
Customers have used SNA APIs for years to build transaction-oriented programs. Conversion of existing SNA applications to IP-enabled applications proves to be uneconomical and very technical due to the complexity of the applications. For this reason, IBM introduced SNA/IP ("SNA over IP") to preserve the investments in SNA.
What are typical SNA Applications?
3270-based applications (Dependent sessions):
In this case, end users communicate with the mainframe using a 3270 program or libraries. Data sent from program (like CICS, IMS) is displayed on 3270 screens.
It is called a dependent session because it an Requires SSCP-LU session to arbitrate LU-LU session startup. For example, 3270 Terminals or Robotic Process Automation with 3270.
Application-to-application (Independent sessions):
In this case, end users send a request using SNA to the Mainframe transaction program. Upon receiving the reply to an inquiry or database update, it returns it on the end user.
It is called an Independent session because it does not need the SSCP. Independent LU6.2 session initiation performed directly by PU2.1 node. For example, a transaction to query account balance.
Advanced Program-to-Program Communication (APPC )
Advanced Program-to-Program Communication or APPC is an implementation of the Systems Network Architecture (SNA) LU 6.2 protocol on a given system. APPC allows interconnected systems to communicate and share the processing of programs. Host Integration Server provides support of APPC via its SNA Gateway feature.
The Host Integration Server (HIS) server product is available to install on Azure Virtual machines. It requires a BizTalk Server license.
HIS technologies are available in Azure Integration Services (AIS) via Azure Logic Apps connectors. The connectors do not require a license as they are part of the Azure Logic Apps product.
The following is a sample Topology of an environment that uses SNA over IP Network with Host Integration Server and Azure Integration Services.
In this video we explain the alternatives to connect from Azure to an IBM Mainframe to interact with SNA Applications. Azure Integration Services helps our customers and partners to connect to IBM Mainframes directly using TCP/IP or via SNA over IP networks.