Command Processing Exceptions; Overlapping Commands - Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications

1) If a command is issued to the logical unit in the sense data hold state by the INIT which is the object
of sense data holding.
– In the case of an untagged command
REQUEST SENSE command:
Other commands:
– In the case of a tagged command
The BUSY status is reported and the sense data hold state is released.
2) If a command is issued to the logical unit in the sense data hold state from an INIT which is not the
object of sense data holding, the sense data hold state is not released and the command is queued.
3) In the following cases, the sense data hold state is released and the sense data being held are lost.
– The RESET condition occurs on the SCSI bus.
– A TARGET RESET message is issued by any INIT.
– An ABORT TASK SET message is issued by an INIT for which sense data held for the logical unit in
the sense data hold state.
1.7

Command Processing Exceptions

1.7.1

Overlapping commands

If the following state occurs, the IDD recognizes that overlapping commands have been generated and the
command is terminated abnormally.
1) During the IDD is executing or queuing an untagged command, the INIT that issued that command
before the completion of the command execution issues either an untagged command or a tagged
command.
2) If the IDD is executing or queuing a tagged command, the INIT that issued that command before the
completion of the command execution issues another tagged command with the same tag specified as
the previous command or an untagged command.
Normally, completion of a command execution is at the point when the TARG notifies the INIT of the
TASK COMPLETE message. Execution of a command can also be terminated by the RESET condition,
a TARGET RESET message, CLEAR TASK SET message, ABORT TASK SET message or ABORT
TASK message.
The IDD abnormally terminates all the commands (commands being executed or queued) received from
an INIT which is overlapping commands and the command that generated the overlap condition by the
procedure described below.
1) If the command received form the INIT is being executed, the IDD stops execution of the command.
If the command is still in the queue and execution has not been started, the IDD clears that command.
C141-C010
1.7 Command Processing Exceptions
The sense data held by the IDD are transferred to the INIT and the
sense hold state is released.
The sense data hold state is released and the command is executed
normally if commands issued from the INIT are not queued. If
commands issued from the INIT are queued, the commands are
treated as overlapping commands.
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