Concepts 
The SAP DB Loader uses the concepts of the SAP DB database instance and also its own concepts.
For the entire
concepts of the SAP DB database, see the Reference Manual: SAP DB 7.4,
Concepts
section. In particular, the SAP DB Loader uses the following
concepts:
The SAP DB Loader provides functions to load, unload, and format (transform) data between different data sources and data targets using different data streams.
The language scope of the SAP DB Loader allows the transformation of the data of all users of a SAP DB database, a user, a table of a user, or a set of qualified columns of a table or multiple tables (Commands for Loading and Unloading).
Media and
database instances
are supported as physical data sources and physical data targets.
The Loader uses metadata, which can be in different formats, for the logical description of data and its transformation.
When the system tables are filled, this can, among other things, be used for restarting a transformation.