The Data and Structure Definition Language (DASDL) is used by the database administrator to describe the physical and logical characteristics of the database, and the criteria to be used to ensure the integrity and security of the data contained within it.

The DASDL compiler (SYSTEM/DASDL) checks the input for proper syntax and produces a file titled DESCRIPTION/<database name>. As illustrated by DASDL Compilation through DMSUPPORT Compilation, the description file is used during compilation of all Enterprise Database Server software and user programs that access the database.