User's Guide

Quantum Scalar Intelligent Libraries SCSI Reference Guide Guide 7
Reserved Fields
Reserved fields are not checked, and no error will be sent if they contain non-zero values.
Vendor Specific Fields
Vendor Specific fields are not checked and no error will be sent if they contain non-zero values, unless
specific uses are defined within a SCSI command and vendor specific settings are required.
Online/Offline Operation
Each Media Changer can be placed in either an online or offline mode. The purpose of these modes is to
configure whether the Media Changer is being controlled by a SCSI initiator or by the local or remote user
interface. When the Media Changer is online, a SCSI initiator is controlling it and all SCSI commands are
supported. When the Media Changer is offline, the local or remote user interface is controlling it, and the
only allowed SCSI commands are INQUIRY, REPORT LUNS, REQUEST SENSE, TEST UNIT READY,
RESERVE, RELEASE and MODE SENSE (page 1Dh). All other commands will respond with a check
condition, along with an ASC/ASCQ of 04/8Dh (Logical unit offline) or 04/12h (Logical unit not ready, offline).
The READ ELEMENT STATUS command is allowed with DVCID=1, VOLTAG=0 while the library is offline
or the main door is open.
The DA Blade Controller Device SCSI command set is not affected by the online/offline mode of the Media
Changer.
Supported Interfaces
The library supports parallel SCSI, SAS and Fibre Channel interface types, supporting parallel SCSI and
Fibre Channel interfaces as described below.
Parallel SCSI Interface Support
The library supports parity checking on the parallel SCSI interface. It will attempt to retry when parity errors
are detected, but if unsuccessful will attempt to respond with a Check Condition indicating in which phase
the parity error was detected.
If permitted by the initiator, the library will also support SCSI disconnect for commands that take a lengthy
time to process, such as MOVE MEDIUM. Disconnect privilege is granted by the initiator via the Identify
message.
Supported Messages
The SCSI message system (Message In/Message Out) allows communication between an initiator and a
target for the purpose of physical path management. The supported messages are shown in the following
table. The direction is relative to the initiator.
Table 6 Supported SCSI Messages
Message Code Direction Description
COMMAND COMPLETE 00h In This message is sent from the target to an initiator
to indicate that the execution of a command
completed and valid status has been sent to the
initiator.