The Loader provides you with functions for unloading, loading, and formatting (transforming) data between different data sources and data targets in different granularities.
The Loader recognizes two types of data:
· Application Data
· Metadata
Application data is the data that is stored in the database tables.
The Loader writes the application data to a data stream when unloading from the database system and to the database system when loading from a data stream.
The database system manages its metadata in the database catalog.
For the Loader, metadata is data that mirrors the database catalog information as well as data that describes the application data, database catalog information, and load and unload processes (transformations) in accordance with the requirements of the Loader.
The Loader recognizes two types of metadata:
· Metadata of the Application Data
· Metadata of the Database Catalog
· Metadata of the Transformation
The metadata of the application data (metadata of the type DATA) is defined in the data streams using commands and SQL statements.
If the transformation spans multiple tables, the Loader stores this information in the system tables.
The corresponding data is stored in the database instance in the form of pages or rows, and in a data stream in the non-readable formats PAGES and RECORDS or in the readable formats COMPRESSED, FORMATTED, and FORMATTED BINARY.
If the data is transformed to the format of rows, columns of the external data type CHAR with the code attribute ASCII can be transformed to values of data fields with the code attribute ASCII, UCS-2, or UTF-8.
Metadata of the database catalog (metadata of the type CATALOG) describes the structure of the data in the database catalog.
If the transformation spans multiple tables, the Loader stores this information in its system tables.
The corresponding data is stored in the database instance in the form of rows in the system tables and in a data stream in the form of SQL statements for data definition.
The metadata of the transformations (metadata of types CONFIGURATION and PACKAGE) is declared in the form of commands or in the form of Loader-specific system tables.
This metadata describes the configuration and the runtime behavior of the transformations that span multiple tables.
The corresponding data, such as user names and table names, is stored, sorted by referential constraint conditions.
In the database instance, the data is stored in the form of rows in the system tables in a data stream in the readable format COMPRESSED.