Record type 19 (X'13') — Direct Access Volume

Record type 19 is written:
  1. For each online device associated with a specific IPL time frame,
  2. For each online device associated with a processed HALT EOD or SWITCH SMF command, and
  3. When a direct access volume that is defined by DD statement is demounted.
This record contains:
  • The volume serial number
  • The volume table of contents (VTOC) address
  • The owner identification
  • The unit type
  • The number of unused alternate tracks
  • The number of unallocated cylinders and tracks
  • The number of cylinders and tracks in the largest free extent
  • The number of unallocated extents.
  • The previous three fields repeated for track-managed space
  • The volume size information
It contains the device number and module identification for devices having movable plugs.
Note:
  1. Record type 19 is not produced for DOS volumes used under the operating system.
  2. In order to determine the latest status of a shared file, the CPU clocks must be synchronized.