Dell PowerVault TL4000 - Manual (Page 103)

No Operation
The NO-OP message is sent from an initiator to inform the target that no message is valid in response to
the target request for a message. The media changer does not take any action in response to the No
Operation message; it accepts this message and continues processing the current command.
Message Parity Error
The MESSAGE PARITY ERROR message is sent from the initiator to the target to indicate that one or
more bytes in the last message received contained a parity error.
Bus Device Reset
The BUS DEVICE RESET message is sent from an initiator to clear all commands, data, and status at the
target. When the target recognizes this message, it aborts the command currently being executed,
proceeds to the BUS FREE state and executes a soft reset.
Identify
The IDENTIFY messages are sent either by the initiator or by the target to establish (or reestablish) the
logical connection path between an initiator and target for a particular logical unit.
Bit 7 6 5 4 3 2 1 0
Byte
0 Identify DiscPriv LUNTAR Reserved LUN
Field Descriptions:
Bit 7 - Identify
This bit must be set to 1 to indicate this is the Identify message.
Bit 6 - DiscPriv (Disconnect Privlege)
This bit indicates whether the initiator supports the disconnect privelege, as follows:
v 0 - Disconnect is not allowed
v 1 - Disconnect is allowed
The media changer always sets this bit to 0. Only initiators indicate if they support disconnect.
Bit 5 - LUNTAR (Logical Unit Target)
This bit indicates the LUNs that you can access on this device. This bit must be set to 0 to
indicate that the Identify message is directed to a logical unit.
Bit 2 ..0 - LUN (Logical Unit Number)
The only supported logical unit number for the media changer is 1. If the LUN fiels is set to a other
value than 0, the media changer returns Check Condition status to commands other than
INQUIRY and REQUEST SENSE, and the sense data is set to indicate that the logical unit is not
supported.
Chapter 4. Messages 4-3