Seagate Ultra 160, Ultra 320 manual Status precedence

Busy. This status indicates that the logical unit is busy. This status shall be returned whenever a logical unit is unable to accept a command from an otherwise acceptable initiator (i.e., no reservation conflicts). The recom- mended initiator recovery action is to issue the command again at a later time.

Intermediate. This status or Intermediate-Condition Met shall be returned for each successfully completed command in a series of linked commands (except the last command), unless the command is terminated with Check Condition, Reservation Conflict, Task Set Full, Busy status. If Intermediate or Intermediate-Condition Met status is not returned, the series of linked commands is terminated and the task is ended.

Intermediate–Condition Met. This status is returned whenever the operation requested by a linked command is satisfied (see the PREFETCH commands in ANSI SCSI Block Commands-2, T10/1417D), unless the com- mand is terminated with Check Condition, Reservation Conflict, Task Set Full, Busy status. If Intermediate or Intermediate-Condition Met status is not returned, the series of linked commands is terminated and the task is ended.

Reservation Conflict. This status shall be returned whenever a SCSI initiator port attempts to access a logical unit or an element of a logical unit that is reserved with a conflicting reservation type for another SCSI initiator. (See the RESERVE, RELEASE, PERSISTENT RESERVE OUT and PERSISTENT RESERVE IN commands in ANSI SCSI Primary Commands - 4, T10/1731-D). The recommended initiator recovery action is to issue the command again at a later time. Removing a persistent reservation belonging to a failing initiator may require the execution of a PERSISTENT RESERVE OUT command with the Preempt or Preempt and Clear actions (see the SPC-4 standard, T10/1731-D).

Task Set Full. This status shall be implemented if the logical unit supports the creation of tagged tasks (see Section 7.7). This status shall not be implemented if the logical unit does not support the creation of tagged tasks.

When the logical unit has at least one task in the task set for a SCSI initiator port and a lack of task set resources prevents entering a newly received tagged task from that initiator in the task set, Task Set Full shall be returned. When the logical unit has no task in the task set for a SCSI initiator port and a lack of task set resources prevents entering a newly received tagged task from that initiator in the task set, Busy should be returned.

When the logical unit has at least one task in the task set and a lack of task set resources prevents entering a newly received untagged task in the task, Busy should be returned.

The logical unit should allow at least one queued command for each supported initiator that has identified itself to the target by a protocol specific procedure or by the successful transmission of a command.

ACA Active. This status shall be returned when an auto contingent allegiance exists within a task set and a SCSI initiator port issues a command for that task set when at least one of the following is true:

a.There is a task with the ACA attribute in the task set;

b.The initiator issuing the command did not cause the ACA condition; or

c.The task created to execute the command did not have the ACA attribute and the NACA bit was set to one in the CDB Control byte of the faulting command (see Section 7.6.1).

The initiator may reissue the command after the ACA condition has been cleared.

Task Aborted. This status shall be returned when a task is aborted by another SCSI Initiator and the Control mode page TAS bit is set to one.

7.3.1Status precedence

If more than one condition applies to a completed task, the report of a Busy, Reservation Conflict, ACA Active or Task Set Full status shall take precedence over the return of any other status for that task.

Parallel SCSI Interface Product Manual, Rev. A 139