(1) In mainframe computing, a data-record format employing self-defining record formats in which each record is represented by up to three fields: a count field identifying the record and specifying its format, an optional key field that can be used to identify the data area contents, and an optional data field that typically contains the user data. See also data record.
(2) An ESA/390 architecture for a direct access storage device (DASD) logical device that specifies the format of and access mechanisms for the logical data units on the device. The logical data unit is a track that can contain one or more records, each consisting of a count field, an optional key field, and an optional data field. See also custom volume.