Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications page 127

3.1 Control/Sense Commands
For the "Reservation Key" field, an 8-byte key code provided by the application client is set in order to
enable the drive to identify the initiator that is the source of the PERSISTENT RESERVE OUT
command. The drive can then verify that the "Reservation Key" field in the PERSISTENT RESERVE
OUT command matches the registered reservation key for the initiator that issues the command.
However, if the reservation key value is zero, which means no reservation key is registered, the specified
value in this field is ignored. If the key specified for the PERSISTENT RESERVE OUT command does
not match the registered reservation key for the initiator, the drive returns the RESERVATION
CONFLICT status. This reservation key of the initiator is valid to all service actions and Scopes.
The "Service Action Reservation Key" field must be specified for the REGISTER, PREEMPT, and
PREEMPT AND ABORT service actions. In the REGISTER service action, a new registered
reservation key is specified in this field. In the PREEMPT and PREEMPT AND ABORT service
actions, a reservation key of the initiator that holds the reservation requirements to be preempted is
specified in this field. In the PREEMPT or PREEMPT AND ABORT service actions, if the value
specified in this field does not match any registered reservation key, the drive returns the
RESERVATION CONFLICT status. In other service actions, the value specified in this field is ignored.
If the Scope is the Element reservation, the "Scope-specific Address" field contains the Element address,
zero filled in the most significant bytes to fit the field. If the service action is REGISTER, REGISTER
AND IGNORE EXISTING KEY, or CLEAR, or if the Scope is a Logical Unit reservation, the "Scope-
specific Address" field is set to zero.
The "Activate Persist Through Power Loss (APTPL)" bit shall be valid only for the REGISTER service
action. In any other service action, the APTPL bit is ignored. Support for the APTPL bit is optional. If
a value is specified for a drive that does not support the APTPL bit, the drive returns the CHECK
CONDITION status and terminates this command. In this case, the sense key is set to ILLEGAL
REQUEST [=5], and sense data is set to INVALID FIELD IN PARAMETER LIST [=26-00].
If the last APTPL bit value received by the driver is zero, all persistent reservations are released and all
reservation keys are cleared by turning off the power to the target (See Section 4.2.1.1). If the last
APTPL bit value received by the driver is one, the logical unit keeps all persistent reservations and
reservation keys for all initiators even after unit power is turned off once and turned on again.
(MA*3*** series product saves the registration information in the SA space.) The APTPL value
controls the operation of the logical unit while power is off, and it is always valid even if it is received
from an initiator.
Table 3.4 summarizes which fields are defined by the application client and interpreted by the drive for
each service action and scope value. The reservation keys and APTPL are explained in previous
sections.
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