For Oracle (with Appx 4.2.8):

Appx field type = Alpha or Logic

        if the field is a key segment , Appx builds a CHAR(n) column

        if the field is less than 6 character long, Appx builds a CHAR(n) 

        otherwise, Appx builds a VARCHAR(n) column

Appx field type = Date

        for CCYYMMDDhhmmss key segments, Appx builds a VARCHAR(14) column

        for CCYYMMDDhhmmss non-key fields, Appx builds a DATE column

        for all other date components,  Appx builds a VARCHAR(n) column

Appx field type = Numeric (binary)

        if field length = 1, Appx builds a NUMBER( 3, 0 ) column

        if field length = 2, Appx builds a NUMBER( 5, 0 ) column

        if field length = 4, Appx builds a NUMBER( 10, 0 ) column

Appx field type = Numeric (packed)

        Appx builds a NUMERIC( x, y ) column