User's Guide

Chapter 1 Theory of Operation
SCSI-2 Implementation Philosophy
2 Quantum DX-Series Software Interface Guide
SCSI-2 Implementation Philosophy 1
Using the SCSI-2 standard, the DX-Series system is designed so that the
host can adapt to changes in the configuration. For example, the host can
detect a change in the number of virtual tape drives configured in the DX-
Series system.
The DX-Series system uses the SCSI-2 medium changer command set.
This command set is complete and includes all primitive (elemental)
commands required by a host to carry out any required complex
operation.
The DX-Series system relies on the host computer to perform complex
operations by issuing a sequence of elemental commands in the correct
order. The DX-Series system does not execute operations that could result
in damage to the device.
Medium Changer Elements 1
The medium changer command set accesses address space for the set of
physical locations and mechanisms within the DX-Series system. This
guide uses the SCSI-2 term element to refer to one member of the DX-
Series system address space.
Each element is a discrete physical entity that can hold a single tape
cartridge and is represented by a unique 16-bit element address.
The DX-Series system consists of these medium changer elements:
• Medium transport element
• Storage elements
• Data transfer elements
Issue the Mode Sense command to determine:
• DX-Series system configuration
•First address
• Number of elements of each type (medium transport, storage, or data
transfer)