SQL LOADER is an Oracle utility used to load data into table given a datafile which has the records that need to be loaded.
SQL*Loader takes data file, as well as a control file, to insert data into the table. When a Control file is executed, it can create Three (3) files called log file, bad file or reject file, discard file.
Log file tells you the state of the tables and indexes and the number of logical records already read from the input datafile. This information can be used to resume the load where it left off.
Bad file or reject file gives you the records that were rejected because of formatting errors or because they caused Oracle errors.
Discard file specifies the records that do not meet any of the loading criteria like when any of the WHEN clauses specified in the control file. These records differ from rejected records