A tape mark must follow each data set and data set label group. Tape marks cannot exist within a data set. When a program writes data on a standard labeled or unlabeled tape, the system automatically reads and writes labels and tape marks. Two tape marks follow the last trailer label group on a standard-label volume. On an unlabeled volume, the two tape marks appear after the last data set.

When a program writes data on a nonstandard labeled tape, the installation must supply routines to process labels and tape marks and to position the tape. If you want the system to retrieve a data set, the installation routine that creates nonstandard labels must write tape marks. Otherwise, tape marks are not required after nonstandard labels because installation routines manage positioning of the tape volumes.