Disk label
With volume label ( English for Volume label ), and volume label, the header data (tape are header ) in sequential media such as magnetic tapes referred to in mainframe computers were used by IBM and other companies. You are in the first logical and physical entry.
Details
So-called file labels were used in the 1960s to the mid-1990s in order to identify and organize sequential data carriers themselves and the stored files . The labels were only 80 bytes long and could therefore be used on punch cards as well as on magnetic data media, mainly magnetic tapes. Each data carrier (stack of punched cards or magnetic tape or disk / disk stack) has a VOL label ( volume ) which shows the owner, the name of the data carrier (possibly with a sequence number) and the date of creation. If several data carriers belong to a data stock, the EOV label (End-Of-Volume) shows the next sequence number of a data carrier or the end. The VOL label was sometimes referred to as the volume label.
A file is identified by an HDR label (header) that shows the name of the file, version number, creation date, creator, and expiry date. After the HDR label, a series of USRn labels (User Label 1 to n) can follow before the actual user data begins.
A file is closed with an EOF label i. d. Usually a "/ *".
In the headers, the structure of the file (record form fixed or variable) and the blocking (fixed or variable) as well as the respective lengths were also specified.
References should be provided by the system literature on the mainframe systems of the time, e.g. B. IBM 360 or IBM 370 or Siemens 4004 with the operating system (Siemens) BBS, BPBS, PBS, later BS1000 and BS2000.
IBM speaks of the System 360 volume labels, which consist of volume labels (VOL1) and end of volume labels (EOV). Then there are data volume labels with prefixes (header, HDR) and suffixes (end of file, EOF). User labels are called User Header Label (UHL), the suffixes User Trailer Label (UTL). Tape marks (BM) are placed between some labels. A punch card VOL1 consists of: Bytes 1-4: "VOL1", Bytes 5-10: Serial number of the data carrier, Byte 11: Security information, Bytes 12-41: Blank, Bytes 42-51: Name / address of the owner, Bytes: 52 -80 empty. Another punch card is required for the header.
A magnetic tape with several amounts of data then looks like this:
VOL1-8, HDR1-8, UHL1-8, BM, Daten size, BM, EOF1-8, UTL1-8, BM, HDR1-8, UHL1-8, BM, Daten size, BM, EOF1-8, UTL1-8, BM, BM, ...
Siemens also speaks of reel labels for the System 4004. Tape head labels are created with the TPINIT (disk operating system PBS) command. Byte 4 of the VOL punch card consists of the number of the reel label number for other tapes. Bytes 72-80 can optionally contain the card number of the VOL card. If there are several bands, the U-card control card is used, which contains details and the number of additional bands. At the end there is the ENDV card.
Other meanings
With a data carrier label, a self-adhesive label z. B. on a CD. Volume label appears with a different meaning in other systems, such as DOS (hard disk label via command vol in the FAT).
emulation
In the well-known Hercules emulator , the data can be viewed with the HETMAP program .
See also
- Volume Table Of Contents (VTOC), direct access method for DASD tapes
Web links
- Volume label in the IBM Knowledge Center (z / OS)
- MARC-1 specifications ANSI X3.27-1978 at loc.gov
- MVS / ESA Magnetic Tape Labels and File Structure Administration, IBM Norm SC26-4511 PDF on Classiccomp