Preprocess clause External Tables - ORACLE_LOADER Access Driver

External tables exists since Oracle version 9i, enable to view a file as if it were data in a database. To simplyfy the Extract, Transform, and Load (ETL) processes oracle had added a parameter PREPROCCESS  to sqlloader for extrations by external tables. The PREPROCESSING  parameter is introduced in Oracle version 11Gr2 which allow ETL processes handle any type of file without additional out-of-line action. (For example execute a shell script, unzip).