Networking on z/OS
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TN3270 Enhanced

Networking on z/OS

The TN3270E protocol represents the evolution of SNA as it converged into the world of TCP/IP. It is the primary method of connecting end users to mainframe computers. It consists of a character-based data stream. TN3270E connectivity is handled on the mainframe by the TN3270E server. The TN3270E server converts a TN3270E TCP/IP connection to an SNA session. The terminal LU of the SNA session is emulated so that the SNA application functions as though it were connected to a non-programmable 3270 terminal.

  • Introduction to the 3270 terminal
    During the last several decades, before the Internet Protocol's rise in popularity, large organizations established their own SNA networks. These SNA networks were used to communicate between remote end-users and the centralized mainframe. The display management protocol used to facilitate this communication within an SNA environment was called the 3270 data stream. At the end user's location in an SNA network was a device referred to as a 3270 terminal.
  • TN3270 Enhanced (TN3270E)
    Today, a single instance of the TN3270E server can support up to 128 000 emulated 3270 display terminals.
  • Where to place a TN3270E server
    The connection from the TN3270E server to the target application is "normal" SNA protocol and, because of this, the target application could actually be anywhere within the SNA network–on another mainframe host in the organization, or even in another organization.
  • TN3270E server implementation
    You can implement TN3270 in z/OS Communications Server either within the TCP/IP address space or, beginning with z/OS V1R6, in its own address space. The definitions of the TN3270E server are identical in both configuration alternatives. However, when running the TN3270E server as its own task, the definitions for the TN3270E server cannot be placed in the TCP/IP profile data set.
Parent topic: SNA and SNA/IP implementation on the mainframe
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