It is the consecutive processing that extraction (extract) it does the data from the data source of the basic type business system and the like, necessary conversion processing (transform) does, the load (load) does in the target system of the data warehouse and the like. There are also times when it points to the software tool which supports that.

When the data warehouse is constructed, many of all the development man-hours are spent to ETL development also to be said, if in addition there is modification in either one of the source system and the target systems, various maintenance jobs occur.

The ETL tool, correction of the illegitimate data (data cleansing), is a function of calculation, conversion and the load etc. of the integration, summary and guidance data, is useful to the decrease of development man-hour management man-hour