ISO/IEC 4909:2006 recognizes the need for formats of track 3 which can be used independently of, or in conjunction with, track 2 as defined in ISO/IEC 7813. This approach is intended to permit the greatest degree of flexibility within the financial community in facilitating international interchange.
Using track 3 in conjunction with track 2 is a mode of operation in both on-line and off-line interchange environments. This mode of operation requires that the original encoded data on track 2 be read; the data on track 3 be read; and, if update is required, all the data on track 3 be rewritten.
Independent use of track 3 is an alternative mode of operation permitting both on-line interchange and off-line interchange based on mutual agreement between interested parties. It requires reading only of the data on track 3 and, if update is required, the rewriting of all the data on track 3.