DDS has built-in capabilities to handle physical devices (tape and disk drives) directly. There are special Device Attributes associated with these devices. For example, tape drives have labels, density, lengths, and block sizes. Attributes supported by DDS are described. The end user is normally concerned with only a few keyword attributes. They are label, dsn, merge, online, and offline.

Device attributes are controlled by device Definitions. The device name itself is used in place of an input or output filename. Then a Definition with the name of that device is used to specify the device attributes. This following example assumes multiple reels of tape are input. Traces from all reels are concatenated together. If a reel has multiple files, they are merged.

in_data= /dev/rst0b
/dev/rst0b= merge label "RE2201 RE2202 RE2203"