Extract, Transform, and Load (ETL) is a process in data warehousing that involves extracting data from outside sources, transforming it to fit business needs (which can include quality levels), and ultimately loading it into the end target, i.e. the data warehouse. ETL can also be used for the integration with legacy systems. Usually ETL implementations store an audit trail on positive and negative process runs. In almost all designs, this audit trail is not at the level of granularity which would allow the reproduction of the ETL's result if the raw data were not available.
While an ETL process can be created using almost any programming language, creating them from scratch is quite complex. Increasingly, companies are buying ETL tools to help in the creation of ETL processes. A good ETL tool must be able to communicate with the many different relational databases and read the various file formats used throughout an organization.
EAPT provides expert consulting for tools like DataStage and Informatica.