Several iucvtty instances can run to provide multiple terminal devices.
The instances are distinguished by a terminal ID that is set when an iucvtty instance is started.
Figure 1. Login through iucvtty
instances
Connection requests are created with the iucvconn program on the terminal server. A request includes the z/VM® user ID of the target z/VM guest virtual machine and a terminal ID. After successfully connecting to the target system, a communication path is established to the iucvtty instance with the specified terminal ID.
A systemd instance unit, an inittab entry, or an Upstart job file starts the iucvtty instance which, typically, runs a login program.