Extract Transform and Load [Oracle Warehouse Builder]

The first part of an ETL process involves extracting the data from the source systems. Most data warehousing projects consolidate data from different source systems. Each separate system may also use a different data organization / format. The transform stage applies a series of rules or functions to the extracted data from the source to derive the data for loading into the end target. Some data sources will require very little or even no manipulation of data. In other cases, one or more of the following transformations types may be required to meet the business and technical specifications. The load phase loads the data into the end target, usually the Data Warehouse (DW). Depending on the requirements of the organization, this process varies widely. Some data warehouses may overwrite existing information with cumulative, updated data every week, while other DW (or even other parts of the same DW) may add new data in an incremental form, for example, hourly. The timing and scope to replace or append are strategic design choices dependent on the time availability and the business needs. More complex systems can maintain a history and audit trail of all changes made to the data loaded in the DW.