Seagate SCSI Interface Product Manual page 174

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[2] The Service Action Reservation Key field contains information needed for three service actions; the Reg-
ister, Preempt, and Preempt and Clear service actions. For the Register service action, the Service Action
Reservation key field contains the new reservation key to be registered. For the Preempt and Preempt
and Clear service actions, the Service Action Reservation key field contains the reservation key of the
persistent reservations that are being preempted. For the Preempt and Preempt and Clear service
actions, failure of the Service Action Reservation key to match any registered reservation keys shall result
in the device server returning a Reservation Conflict status. The Service Action Reservation key is
ignored for all service actions except those described in this paragraph.
[3] If the Scope is an Element reservation, the Scope-specific Address field shall contain the Element
address, zero filled in the most significant bytes to fit the field. If the Service action is Register or Clear or
if the Scope is a Logical Unit reservation, the Scope-specific address field shall be set to zero.
[4] The Activate Persist Through Power Loss (APTPL) bit shall be valid only for the Register service action. In
all other cases, the APTPL shall be ignored. Support for an APTPL bit equal to one is optional. If a device
server that does not support the APTPL bit value of one receives that value in a Register service action,
the device server shall return a Check Condition status. The sense key shall be set to Illegal Request and
additional sense data shall be set to Invalid Field in Parameter List.
If the last valid APTPL bit value received by the device server is zero, the loss of power in the target shall
release all persistent reservations and remove all reservation keys (see Table 115, register description). If
the last valid APTPL bit value received by the device server is one, the logical unit shall retain all persis-
tent reservations and all reservation keys for all initiators even if power is lost and later returned. The most
recently received valid APTPL value from any initiator shall govern logical unit's behavior in the event of
power loss.
Table 117 summarizes which fields are set by the application client and interpreted by the device server for
each Service Action and Scope value. Two Persistent Reserve Out parameters are not summarized in Table
117; Reservation key and APTPL, since they are specified in Table 116.
Table 117: Persistent Reserve Out Service Actions and valid parameters
Allowed
Service Action Scope
Register ignored
Reserve LU
Reserve Extent
Reserve Element
Release LU
Release Extent
Release Element
Clear ignored
Preempt LU
Preempt Extent
Preempt Element
Preempt and clear LU
Preempt and clear Extent
Preempt and clear Element
Parameters
Service Action
Type Reservation Key
ignored valid
valid ignored
valid ignored
valid ignored
valid ignored
valid ignored
valid ignored
ignored ignored
valid valid
valid valid
valid valid
valid valid
valid valid
valid valid
SCSI Interface Product Manual, Rev. J
Element or
Element Parameters
ignored
ignored
Extent valid
Element valid
ignored
Extent valid
Element valid
ignored
ignored
Extent valid
Element valid
ignored
Extent valid
Element valid