The ISO/ANSI standard data set label 1 (HDR1/EOV1/TRL1) is 80 characters in length and is used to identify each data set. The system records the data set label in ASCII.
| Offset | Data type | Length | Contents | File Type |
|---|---|---|---|---|
| 0 | 3 | Label identifier | ||
| 3 | 1 | Label number | ||
| 4 | Character | 17 | File Identifier | |
| 21 | Character | 6 | File Set Identifier | |
| 27 | Character | 4 | File Section Number | |
| 31 | Character | 4 | File Sequence Number | |
| 35 | Character | 4 | Generation Number (not used) | |
| 39 | Character | 2 | Version Number (not used) | |
| 41 | Character | 6 | Creation Date | |
| 47 | Character | 6 | Expiration Date | |
| 53 | Character | 1 | Accessibility | |
| 54 | Character | 6 | Block Count, Low Order (Trailer labels only) | |
| 60 | Character | 13 | System Code (Trailer labels only) | |
| 73 | Character | 7 | Reserved |
The manual describes the contents and function of each of the following fields.
The relative position of this label within the set of labels of the same type; it is always 1 for the data set label 1.
A unique identification code to identify the data set (file). If the data set ID is less than 17 characters, it is left justified and padded with blanks.
This field contains the volume identifier from the volume labels of the first volume in a multivolume data set.
This field contains the relative volume number of this volume in a multivolume data set. The field is 0001 for a single volume data set.
This field indicates the relative position of the data set within a multiple data set group. The value will be in EBCDIC displayable characters for 0001–9999. For numbers larger than 9999 that will not fit in the 4–character field as an EBCDIC displayable character set, the first byte will a '?' ('6F'x for EBCDIC labels. The last three bytes will be a binary number from 1 to 64000.
If the data set is a part of a generation data group, this field contains a number that indicates an absolute generation number. i5/OS™ does not use this field.
If the data set is part of a generation data group, this field contains a number indicating the version number of the generation. i5/OS does not use this field.
The creation date of the data set. the program shows the date in the format cyyddd, where:
c = century (blank=19; 0=20; 1=21; and so on)
yy = year (00-99)
ddd = day of the current year (001-366)
Note that the century code gives the first two digits of the year, not the actual century. For example, a blank which translates into 19 indicates a year in the 1900s, not in the nineteenth century.
The program considers the date in which the data set expires. Expired refers to a data set being allowed to be overwritten. The user specifies the date in the open tape file used in writing the tape. The i5/OS ignores the expiration date on input, and verifies the expiration date on output. The date is in the format cyyddd, where:
c = century (blank=19; 0=20; 1=21; and so on)
yy = year (00-99)
ddd = day of the current year (001-366)
Note that the century code gives the first two digits of the year, not the actual century. For example, a blank which translates into 19 indicates a year in the 1900s, not in the nineteenth century.
The field in the trailer labels contains the number of data blocks in the data set on the current volume. The field in the header labels contains hex zeros.