The ORACLE_LOADER access driver attempts to divide large data files into chunks that can be processed separately.
The following file, record, and data characteristics make it impossible for a file to be processed in parallel:
Sequential data sources (such as a tape drive or pipe)
Data in any multibyte character set whose character boundaries cannot be determined starting at an arbitrary byte in the middle of a string
This restriction does not apply to any data file with a fixed number of bytes per record.
Records with the VAR format
Specifying a PARALLEL clause is of value only when large amounts of data are involved.