Using the unit verification service

The information in this topic describes using the unit verification service to obtain information from the eligible device table. IBM® recommends that you use the EDTINFO macro instead; EDTINFO provides more services and is easier to use than the unit verification service.

EDTINFO must be used to obtain information on units that are defined as:

Dynamic,
Have 4-digit device addresses, or
Are described by unit control blocks (UCBs) that reside above the 16-megabyte line.

The IEFEB4UV routine interface maybe used, only, to obtain information on units that are static, have 3-digit device addresses and are described as UCBs residing below the 16-megabyte line.

The unit verification service enables you to obtain information from the eligible device table (EDT) and to check your device specification against the information in the EDT. See z/OS HCD Planning for information on the EDT.

There are three versions of the unit verification service:

IEFEB4UV, for problem programs or authorized callers.
IEFGB4UV and IEFAB4UV, for authorized callers.

Note: IEFEB4UV is the preferred interface.