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ACA is a condition that is created within the Target task set whenever CHECK CONDITION is returned. While it exists, all
tasks in the task set are blocked (i.e., the queue is frozen). New tasks from Initiators other than the faulted Initiator are not
entered into the task set and are completed with a status of ACA ACTIVE.
New tasks from the faulted Initiator are entered into the task set under two different conditions, depending on the state of the
NACA bit in the CDB Control Byte of the faulting command.
1. If the NACA bit was set to 0b, the previously described SCSI-2 CA rules apply.
2. If the NACA bit was set to 1b, the new task must have the ACA attribute and there must be no other task in the task set
with the ACA attribute. If these conditions are not met, the task is completed with a status of ACA ACTIVE.
Note: Only NACA = 0b is supported.
18.5.3 Autosense
Autosense is the automatic return of sense data upon completion of the task. It is equivalent to an explicit REQUEST SENSE
command being executed immediately after Check Condition status is returned.
The sense data is returned in the I4 FCP_RSP IU. The FCP_SNS_LEN field indicates how many bytes of valid sense are con-
tained in the FCP_SNS_INFO field.
Hitachi Ultrastar 15K450 (FC-AL) Hard Disk Drive Specification
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