Defining devices

You need three steps to define an I/O device:

• Define device characteristics and control unit connection
• Define CSS-related definitions for a device
• Define OS-related definitions for a device (including EDT and esoteric group assignment - MVS-type only).

Before you define a device that should be defined to an operating system and to the channel subsystem (CSS), you must have defined the operating system configuration, processor, channel path, and control unit. HCD omits some steps if data is missing. For example:

• You cannot define the processor data for the device if the device is not attached to a control unit or the control unit is not attached to a processor.
• You cannot define the EDT/esoteric group data for the device until you have defined an EDT for the OS.