Virtual Telecommunications Access Method
VTAM (English Virtual Telecommunications Access Method) is a product of IBM. It is one of two known implementations of a so-called SSCP (English System Services Control Point) or Physical Unit Type 5 (PU Type 5 ) dar. This SSCP is the hierarchically highest or central network nodes within the SNA ( Systems Network engl. architecture ). The second implementation of SSCP is TCAM (English Telecommunications Access Method ), which can be considered a predecessor of VTAM.
VTAM provides, inter alia, a programming interface ( API) that implements functions for communicating with devices for remote data transmission and their users. It was developed in the 1970s.
VTAM enabled programmers for the first time to treat the device as a "logical unit " and control without detailed knowledge of the hardware of the individual devices or protocols used. Prior to the development of VTAM BTAM was used the Basic Telecommunications Access Method.