D

database

(1) A collection of data with a given structure for accepting, storing, and providing on demand, data for multiple users. (2) A collection of interrelated data organized according to a database schema to serve one or more applications. (3) A collection of data fundamental to a system. (4) A collection of data fundamental to an enterprise.

data link control (DLC)

In SNA, the protocol stack layer that transmits messages across links and manages link-level flow and error recovery.

data set members

Members of partitioned data sets that are individually named elements of a larger file that can be retrieved by name.

deallocate

(1) The process an operating system uses to free memory previously allocated by a program. (2) In APPC, a verb that ends a conversation. Contrast with allocate.

distributed function terminal (DFT)

A type of intelligent terminal supported by IBM 3270 control units, in which some of the terminal's functions are controlled by the terminal and others by the control unit. It allows multiple sessions and connects to host systems or to peer systems through host systems. DFTs are often connected using coaxial cable.

directory

(1) A list of files that are stored on a disk or diskette. A directory also contains information about the files such as size and date of last change. (2) A named grouping of files in a file system.

display verb

An APPC verb that returns configuration information and current operating values for a computer running SNA Server.

DL-BASE

The type of Base used by SNA Server 3270 emulation programs. It supports a single SNA Server component or a single user application and has entry points for initialization, sending messages, receiving messages, and termination. See also Base.

Dynamic Access Module (DMOD)

An SNA component that provides the communications facilities needed to pass messages between the Bases.

dynamic locality

A locality in a SNA Server system where the localities are not configured in advance. In this type of system the relationships between localities are configured dynamically as localities enter and leave the system. See also locality.