Command Processing During Execution Of Active I/O Process - IBM Ultrastar 36LZX Specifications

11.1.4 Command Processing during execution of active I/O process

When the Target is not executing any active I/O processes, a new I/O process is permitted to execute
(unless execution is prevented by another internal Target condition listed in 11.1.1, "Priority of SCSI
Status Byte Reporting").
If an active I/O process does exist when the Target receives a new command, then the Target deter-
mines if
Ÿ Check Condition Status with Sense Key = Aborted Command is returned for an Overlapped Com-
mands Attempted error
Ÿ the command is permitted to execute
Ÿ the command is added to the command queue
Ÿ Queue Full Status is returned
Ÿ Busy Status is returned
If an active I/O process does exist when the Target receives a new command, then the Target deter-
mines how the new command should be handled based on the following rules:
Ÿ Check Condition Status is returned with Sense Key set to Aborted Command for an Overlapped
Commands Attempted error if
- See 11.1.3, "Incorrect Initiator Connection."
Ÿ the command is permitted to execute if
- the command is an Inquiry or Request Sense command
Ÿ Check Condition Status is returned with Sense Key set to Logical Unit Not Ready if
- the startup operation or format operation is an active process.
Ÿ the command is permitted to execute if
- the conditions to execute concurrently are met. (See 11.5, "Concurrent I/O Process.")
Ÿ the command is added to the command queue for an I_T_L nexus if
- no Queue Tag message was received during the connection which established the I/O process,
and
- disconnection is allowed for the current I/O process, and
- there is no queued I/O process or active I/O process corresponding to the I_T_L nexus for the
current I/O process, and
- the command is not linked to a previous command.
Ÿ the command is added to the command queue for an I_T_L_Q nexus if
- a Queue Tag message was received during the connection which established the I/O process,
and
- Tagged Queuing is enabled (DQue = 0), and
- an I/O process (either active or queued) exists at the Target for this Initiator, and
- disconnection is allowed for the current I/O process, and
- there is no queued I/O process or active I/O process corresponding to the I_T_L_Q nexus for the
current I/O process, and
- the command is not linked to a previous command.
Ultrastar 36LZX hard disk drive specifications
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