A switched SDLC line between two NCPs can be used to connect two VTAM® domains. One or more of switched lines can be defined as a switched line group in an NCP major node definition. Associated with each line in the NCP major node definition is a PU definition statement to represent a port for the actual physical unit that can be connected to the NCP on that line. The actual physical units must be defined to VTAM in the switched major node.

The PU definition statements in the switched major node define subareas attached over switched lines that can be dialed in to or dialed out from a communication controller using NCP. These lines are defined in switched line groups in an NCP major node and a VTAM switched major node. For dial-out operations, the PATH definition statement defines the possible paths to be used to establish connection between the communication controller or host processor and the other subarea.