Verification of First Record

The system reads the first record on the tape under the following conditions:

If you use a single-density 9-track tape unit, the record is read in the density (800 bpi, 1600 bpi, or 6250 bpi) of the unit. If the record cannot be read, a unit check occurs.
If you use a dual-density 9-track tape unit, the record is read in its existing density, provided that density is available on the unit. If the density is not available, or if the record is a 7-track record, a unit check occurs.
If you use a 7-track tape unit, the first record is read in the density specified by the user and in the translate-on, even-parity mode. If the record is in another density or mode, or is a 9-track record, a unit check occurs. ISO and ANSI do not specify support of 7-track tape for information interchange.
If you use a cartridge unit, the record is read in the density of the unit. If the record cannot be read, a unit check occurs.

Various error conditions can occur when the system verifies the initial record on a tape. The following figures illustrate system actions (when standard labels are specified, when nonstandard labels are specified, and when no labels are specified), resulting from these error conditions.

Figure 1. Verification of First Record When Standard Labels Are Specified

Figure 2. Verification of First Record When Nonstandard Labels Are Specified

Figure 3. Verification of First Record When Unlabeled Tape Is Specified