Quantum 10K II - Manual (Page 195)

SCSI Description
5–128 Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives
PERSISTENT RESERVATION OUT Command (5Fh) (continued)
Table 5–59 PERSISTENT RESERVATION OUT Command’s Service Action
Descriptions (continued)
Code Name Description
03h Clear A PERSISTENT RESERVATION OUT command with a successful Clear service
action removes all persistent reservations for all initiators. All reservation
keys are also removed. Any commands from any initiator that have been
accepted by the device server as non-conflicting continue their normal
executions.
A UNIT ATTENTION condition is established for all initiators for the cleared
logical unit. The sense key is set to UNIT ATTENTION; the additional sense
data is set to RESERVATIONS PREEMPTED.
Note that applications should not use the Clear action service except
during recoveries associated with initiator or system reconfiguration, since
data integrity may be compromised.
04h Pre-empt A PERSISTENT RESERVATION OUT command with a successful Pre-empt
service action removes all persistent reservations for all initiators that have
been registered with the Service action Reservation key specified in the
PERSISTENT RESERVATION OUT command’s parameter list. A persistent
reservation is also established for the pre-empting initiator. Any
commands from any initiator that have been accepted by the device server
as non-conflicting continue their normal executions. If a PERSISTENT
RESERVATION OUT command is sent that specifies a Pre-empt service
action and no persistent reservation exists for the initiator identified by the
Service action Reservation key, it is not an error condition.
A UNIT ATTENTION condition is established for the pre-empted initiators.
The sense key is set to UNIT ATTENTION; the additional sense data is set to
RESERVATIONS PREEMPTED. Commands that follow are subject to the
persistent reservation restrictions set by the pre-empting initiator.
The persistent reservation thus created by the pre-empting initiator is
defined by the Scope and Type fields of the PERSISTENT RESERVATION OUT
command and the corresponding fields of the command’s parameter list.
The registration keys for the pre-empted initiators are removed by the Pre-
empt service action; the reservation key for an initiator that has performed
a Pre-empt service action with its own Reservation key specified in the
Service action Reservation key remains unchanged, although all other
specified releasing actions and reservation actions are performed.
Note that persistent reservations are not superseded by a new persistent
reservation from any initiator except by the execution of a PERSISTENT
RESERVATION OUT that specifies either the Pre-empt or the Pre-empt and
Clear service actions. New persistent reservations that do not conflict with
an existing persistent reservation execute normally. The persistent
reservation of a logical unit or extents having the same Type value are
permitted if no conflicting persistent reservations other than the
reservations being pre-empted are held by another initiator.
(continued)