What is an Access Method Driver?

Access method drivers (AMDs) are programs that provide the communications link between MVSSERV and a PC. Access method drivers on the host and PC work in pairs, passing data between them in a format appropriate to the mode of PC-to-Host attachment. At the host, MVSSERV's access method driver converts requests into CPRBs, sends them to servers, and converts reply CPRBs back into the proper communications format for transmission to the PC.

MVSSERV provides access method drivers that manage communications with PCs attached to the host through an IBM® 3174 or 3274 control unit in:

Distributed Function Terminal (DFT) mode
Control Unit Terminal (CUT) mode

MVSSERV also provides an AMD interface that lets you write and install other access method drivers to support other modes of attachment. Figure 1 shows the position of the AMD interface in the MVSSERV environment.

Figure 1. The MVSSERV Enhanced Connectivity Environment