Invalid Key Data

Any field that is part of a key is never stored as null. (A null key does not have a well-defined position in relation to other keys.) If a key field has an illegal value, the field is stored in the database as described here:

Illegal LOW-VALUES minimum possible value (0 or -99999...)

minimum possible date value (01/01/01)

Illegal HIGH-VALUES     maximum possible value (99999...)

maximum possible date value (database dependent)

Illegal SPACES zero (or 01/01/01 for a date field)