Obtain from the I/O unit developer the values that describe the characteristics of the I/O unit. To describe control units in the UIM, you need values such as I/O concurrency level, channel protocol, and channel attachment capability. To describe devices in the UIM, you need values such as UCB type, generic preference value, device parameters, and device features. See the sample UIM in Sample of a Unit Information Module (UIM) for a list of required parameters.