ETL service comprises of two parts: Staging engine and Storage Service. Staging engine manages staging process for all data received from several source systems. It interfaces with the AWB scheduler and monitor for scheduling and monitoring data load processes. However, Storage Service manages and provides access to data targets in SAP BW and the aggregates that are stored in relational and multidimensional database management systems.
It is true, however, that the extraction technology provided as an integral part of SAP BW is restricted to database management systems supported by mySAP technology and that it does not allow extracting data from other database systems like IBM IMS and Sybase. It also does not support proprietary file formats such as dBase file formats, Microsoft Access file formats, Microsoft Excel file formats, and others. On the other hand, the ETL services layer of SAP BW provides all the functionality required to load data from non-SAP systems in exactly the same way as it does for data from SAP systems. SAP BW does not in fact distinguish between different types of source systems after data has arrived in the staging area. The ETL services layer provides open interfaces for loading non-SAP data.
Extraction at Service Levels
SAP BW can be integrated with other SAP components based on application programming interface (API) service. It provides a framework to enable comprehensive data replication based on data extractors that encapsulate the application logic. Data Extractor fills the extract structure of data source with a data from data source and offers sophisticated handling of changes. In addition to supporting extractors, the service APIs also enable online access via RemoteCube technology and flexible staging for hierarchies. On the other hand SAP provides an open interface called Staging Business Application Programming Interface (BAPI) to extract data from non-SAP sources. BAPI serves the purpose of connecting third- party ETL tools to SAP BW and provides access to SAP BW objects which facilitates use of customer extraction routines. Data can be extracted at the database level by using: DB connect, flat files and XML. DB connect facilitates extraction directly from DBMS. In this the metadata files are loaded by replicating metadata tables and views into the metadatory repository of SAP BW. Data can also be uploaded from flat files by creating routines for extraction of data and XML files can be extracted through XML via Administrator Workbench in SAP BW.
NOTE: SAP BW provides three ways to extract data at the database or file level: DB Connect, flat file transfer, and XML. SAP BW provides flexible capabilities for extracting data directly from RDBMS tables using DB Connect.
