The operating system uses groups of labels to identify DASD volumes and the data sets they contain. Application programs generally do not use these labels directly. DASD volumes must use standard labels. Standard labels include a volume label, a data set label for each data set, and optional user labels. A volume label, stored at track 0 of cylinder 0, identifies each DASD volume.
A utility program initializes each DASD volume before it is used on the system. The initialization program generates the volume label and builds the volume table of contents (VTOC). The VTOC is a structure that contains the data set labels.
See Using Direct Access Labels for information about direct access labels.