During execution, SQL*Loader can create a discard file for records that do not meet any of the loading criteria. The records contained in this file are called discarded records. Discarded records do not satisfy any of the WHEN clauses specified in the control file. These records differ from rejected records. Discarded records do not necessarily have any bad data. No insert is attempted on a discarded record.
A discard file is created according to the following rules:
You have specified a discard file name and one or more records fail to satisfy all of the WHEN clauses specified in the control file. (Be aware that if the discard file is created, then it overwrites any existing file with the same name.)
If no records are discarded, then a discard file is not created.
You can specify the discard file from within the control file either by specifying its directory, or name, or both, or by specifying the maximum number of discards. Any of the following clauses result in a discard file being created, if necessary:
DISCARDFILE=[[directory/][filename]]
DISCARDS
DISCARDMAX
The discard file is created in the same record and file format as the data file. For data files in stream record format, the same record terminator that is found in the data file is also used in the discard file.
You can also create a discard file from the command line by specifying either the DISCARD or DISCARDMAX parameter. See SQL*Loader Command-Line Reference.
If no discard clauses are included in the control file or on the command line, then a discard file is not created even if there are discarded records (that is, records that fail to satisfy all of the WHEN clauses specified in the control file).