ETL Process flow

During Extraction, the desired data is identified and extracted from many different sources,  including database systems and applications. Very often, it is not possible to identify the specific  subset of interest; therefore more data than necessary has to be extracted, so the identification of  the relevant data will be done at a later point in time. After extracting data, it has to be physically transported to an intermediate system for further processing. 

Depending on the chosen way of transportation, some transformations can be done during this  process, too. For example, a SQL statement which directly accesses a remote target through a  gateway can concatenate two columns as part of the SELECT statement. Based on the  requirements, some transformations may take place during the Transformation and Execution  Phase. Through Informatica mappings, the necessary changes and updates of the data are made  using transformations. 

Then in the Load phase the data is loaded in the target. After all the transformations, it has to be  physically transported to the target system for loading the data into the Target.