Label definition and organization
ISO/ANSI labels are similar to IBM standard labels. The principal
differences between ISO/ANSI labels and IBM standard labels are:
- ISO/ANSI labels are written in ASCII characters. IBM standard labels are written in EBCDIC, except on 7-track tape. IBM standard labels on 7-track tape are written in BCDIC.
- IBM standard labels are 80 bytes long. ISO/ANSI labels have a length of 80 bytes or more.
- A maximum of 9 user volume labels can appear in the beginning-of-volume group. Version 4 labels can also have VOL2–VOL9 appearing after VOL1 label in the beginning-of-volume group.
- An unlimited number of ISO/ANSI user labels can be placed at the beginning and end of a file, and they need not be sequentially numbered or lettered.
- The formats of the ISO/ANSI labels VOL1, HDR2, EOF2, and EOV2 are slightly different from the formats of the corresponding IBM labels.
- A maximum of 9 user EOF or EOV labels can appear in the file section label group.
The labels must be recorded in the subset of ASCII characters allowed by ISO/ANSI standards.
For Version 3 the subset of ASCII characters allowed by ISO/ANSI
standards are:
- Uppercase alphabetic
- Numeric
- Space
- Special (specifically, ! " % & ' ( ) * + , - . / : ; < = > ?)
For Version 4 the subset of ASCII characters allowed by ISO/ANSI
standards are the same as for Version 3, except for the addition of
the underscore:
- Uppercase alphabetic
- Numeric
- Space
- Special (specifically, ! " % & ' ( ) * + , - . / : ; < = > ? _)
All fields in Version 3 or Version 4 system labels (VOL1, HDR1, HDR2, EOV1, EOV2, EOF1, and EOF2) are treated as containing meaningful data. This means alphanumeric fields (except Reserved for Operating System fields) are left-justified, with unused positions filled with space characters; Reserved for Future Standardization fields are filled with space characters; numeric fields are right-justified, with unused positions filled with zeros. Date fields may have a leading space character.
The first 4 characters of an ISO/ANSI tape label always identify
the type of label:
- Label Identifier
- Label Definition
- VOL1 - VOL9
- Volume label set (optional; VOL2 - VOL9 not produced by z/OS)
- UVL1 - UVL9
- User volume labels (optional; not produced by z/OS)
- HDR1
- Data set header label 1
- HDR2
- Data set header label 2 (produced by z/OS, but optional for input)
- HDR3 - HDR9
- Optional (not produced by z/OS)
- UHLa
- User header labels (optional; unlimited number permitted)
- EOV1
- End-of-volume trailer label 1 (produced by z/OS, but optional for input)
- EOV2
- End-of-volume trailer label 2 (produced by z/OS, but optional for input)
- EOV3 - EOV9
- Optional (not produced by z/OS)
- EOF1
- End of data set trailer label 1 (produced by z/OS, but optional for input)
- EOF2
- End of data set trailer label 2 (produced by z/OS, but optional for input)
- EOF3 - EOF9
- Optional (not produced by z/OS)
- UTLa
- User trailer labels (optional; unlimited number permitted)
Note: The fourth character of the user header and trailer labels may
be any valid ASCII character as defined above.
Figure 1 and Figure 2 show the position of the labels with various tape volume organizations. User labels (UHL, UTL) and volume labels (VOL2 - 9) are optional.
Figure 1. Volume organization with ISO/ANSI labels (single data set)
Figure 2. Volume organizations with ISO/ANSI labels (multiple data sets)