Because tape volumes can reside either inside libraries or on shelves outside the library, physical procedures for accessing volumes vary according to their location:

• When a library-resident volume is requested, the system mounts it on a tape drive in the tape library containing the volume.
• When a shelf-resident volume is requested, the installation is given the opportunity to enter the volume into a tape library by using the volume not in library installation exit. If the volume is not entered into the library, the system requests the volume be mounted on a nonlibrary device (stand-alone tape drive).
  Note: Shelf storage may be local to the computer facility and, therefore, accessible to the operator, or it may be located at another location.