Most databases have a maximum record length and the field you are trying to assign would make the record length exceed that value. To add the field causing the problem, you most make more room in the record. If you are creating a new database this can be done by deleting some other fields or reducing the field length of one or more alphanumeric fields (their field length is displayed in the curly braces after the A). To change the length you must delete the field and re-add it. The maximum length of an alphanumeric field is 255, but your database type may reduce this. For more information on creating database fields click on Creating Databases.
If you are adding fields to an existing database, you can create more record room by reducing the field length of newly added alphanumeric fields or by not including all the old fields in the new database. Remember however, that data will be lost in any old fields not moved to the new list. For more information on adding fields to existing databases, click on Adding Database Fields.