No matter what you do, a 3174 will NOT ever work with VM TCPIP. The definitions Ray Noal gave you are for z/OS TCP. VM TCP has no support for using VTAM to drive devices.
To explain the message you asked about, a CETI device presents 3 separate addresses (read, write and control). When you define 620, VM TCP assumes that 620 is the control address, 621 is read, and 622 is write. A 3174 is not a CETI device, so the error is meaningless.
