CHAR and Always Required
Every ODAG field is a character field that must contain a value.
Each column in the record layouts is listed with Field Type CHAR and marked Always Required. Characters are required in all requested fields unless otherwise specified, which is why inapplicable fields carry None rather than being left blank.
Sources: ODAG protocol, Universe Submissions, PDF p. 15; all record layouts, PDF pp. 17-46; CDAG protocol, Universe Submissions, p. 15; all record layouts, pp. 16-59; SNPCC protocol, Universe Submissions (PDF p. 8); field type column of all record layouts (PDF pp. 9-21); FA protocol, record layouts Field Type column, PDF pp. 10-27; FA protocol, Universe Submissions, PDF p. 8; record layouts Field Type column, PDF pp. 10-27; CPE protocol, Universe Submissions and COA guidance, p. 12; COA record layout Field Type column, pp. 13-15.