An exposure is a device extension that enables an MVS system to
perform multiple concurrent I/O operations to the device.
The storage unit uses two
types of exposures:
- Base exposure: A device number that
is associated with a parallel access volume (PAV). It is used
for query, data control, and data access operations.
- Alias exposure: A device number that
is associated with a base exposure and that represents the same logical volume
as the base device number. It is used for data access I/O operations, query,
and control operations.