It is possible that invalid dates can be incorrectly written to the database. Invalid dates are written as NULL, but if the date is in the key, problems can occur. To avoid invalid date problems in this instance, use the 4GL_MAX_DATE configuration variable to set the high-value date.
The format is:
4GL_MAX_DATE = YYYYMMDD
The maximum date for 4GL_MAX_DATE is “20991231” (December 31, 2099).
See also: 4GL_MIN_DATE configuration file variable