Extended Contingent Allegiance Condition - Maxtor ATLAS 10K IV User Manual

5.5

Extended Contingent Allegiance Condition

Under SCSI-2 processing, the Extended Contingent Allegiance condition extends
Contingent Allegiance handling so the initiator has explicit control over the point at
which suspended (queued) commands are resumed. It allows the initiator to send a
REQUEST SENSE command and then send the non-tagged commands to access the
drive's medium.
This action is provided to fix damage left by the failed command before permitting
the drive to continue with processing the queued commands.The Extended
Contingent Allegiance condition is enabled and disabled by the EECA bit in the
MODE SELECT Control Mode page. The Extended Allegiance Condition differs
from the Contingent Allegiance in that, under the Extended Contingent Allegiance
condition:
• The drive sends an INITIATE RECOVERY message to the allegiance
initiator prior to returning the failed command's COMMAND
COMPLETE message. If the initiator rejects the INITIATE
RECOVERY message, the drive drops back to contingent allegiance
level of operation for the current error.
• An ABORT message does not terminate the extended contingent
allegiance condition.
• Non-tagged drive access commands from the "allegianced" initiator are
accepted by the drive and take priority over all queued commands.
QUEUE FULL status is returned if the host sends a tagged command.
• The drive delays resuming or aborting the queued commands until a
RELEASE RECOVERY message is received from the initiator.
The Extended Contingent Allegiance condition remains in effect until cleared by one
of the following:
• Hard reset
• BUS DEVICE RESET message from any initiator
• RELEASE RECOVERY message from the "allegianced" initiator
SCSI Description
Maxtor Atlas 10K IV 5-9