June 24, 2012 \ Ananth TM \ 1 Comment ETL vs ELT – What and Why? Extract – The process by which data is extracted from the data source Transform – The transformation of the source data into a format relevant to the solution Load – The loading of data into the warehouse ETL ELT Strengths · Only relevant data is stored · Easier project management as project can be broken down to smaller chunks · Potentially reduces development time and processing overhead · Utilize existing database engines and reduce hardware costs · Future proof as all data from sources is available Weaknesses · Leaving out irrelevant data may require more changes (costs) at later times · Not a matured concept, so have to deal with learning curve · Additional hardware and skills investment to run 3rd party ETL software · Limited availability of 3rd party tools, database provided engines or ETL tools have to be reutilized Most of the current warehouse systems use the ETL methodology. Some emphasis has been placed on switching to ELT to save development costs, time and risk.Many organizations have recognized the benefits that can be gained from the employment of ELT. In spite of having already deployed warehouse solutions that use ETL, they have embarked upon a process of re-engineering their solutions using ELT through the use of effective tools. Whilst data warehouse development traditionalists will undoubtedly pour scorn on the ELT approach, the clear and obvious benefits cannot afford to be ignored.