If the load statement contains DEFAULT NULL conditions, the file option NULL can be used. This option determines which string is to represent the NULL value.
The NULL string must be specified after the keyword NULL and must be enclosed in single quotation marks. Its maximum length is 20 characters. When comparing the NULL string with the file fields of different lengths, the shorter value is padded with blanks.
If the NULL option is omitted, the corresponding value of the SET parameters is taken.