By default, the data file is in the character set defined by the NLS_LANG parameter. The data file character sets supported with NLS_LANG are the same as those supported as database character sets. SQL*Loader supports all Oracle-supported character sets in the data file (even those not supported as database character sets).
For example, SQL*Loader supports multibyte fixed-width character sets (such as AL16UTF16 and JA16EUCFIXED) in the data file. SQL*Loader also supports UTF-16 encoding with little-endian byte ordering. However, the Oracle database supports only UTF-16 encoding with big-endian byte ordering (AL16UTF16) and only as a database national character set, not as a database character set.
The character set of the data file can be set up by using the NLS_LANG parameter or by specifying a SQL*Loader CHARACTERSET parameter.