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SCSI Description
Maxtor Atlas 10K III 5-101
Table 5-121 presents the definitions of the characters of the available “Type” values
from the Type field of the PERSISTENT RESERVATION IN Read Reservations
parameters.
Each of the codes provides handling instructions for READ operations, for WRITE
operations, and for subsequent attempts to establish persistent reservations (referred to
as “Additional Reservations Allowed” in the table).
05h
Pre-empt &
Clear
A PERSISTENT RESERVATION OUT command with a Pre-empt & Clear service
action removes all persistent reservations for all initiators that have been regis-
tered with the Service action Reservation key specified in the PERSISTENT
RESERVATION OUT command’s parameter list. It also establishes a persistent
reservation for the pre-empting initiator. Any commands from the initiators be-
ing pre-empted are terminated as if an ABORT TASK management function had
been performed by the pre-empted initiator. If a PERSISTENT RESERVATION
OUT command is sent that specifies a Pre-empt & Clear service action and no
persistent reservation exists for the initiator identified by the Service action
Reservation key, it is not an error condition. If the key is registered, however,
the Clear portion of the action executes normally.
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 RES-
ERVATIONS PREEMPTED. Commands that follow, and retries of commands
that timed out because there were cleared are subject to the persistent reser-
vation 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 com-
mand and the corresponding fields of the command’s parameter list.
The Pre-empt & Clear service action clears any ACA or CA condition associated
with the initiator that is pre-empted and clears any tasks with an ACA attribute
from that initiator.
Any Asynchronous Event Reporting operations in progress that were initiated
by the device server are unaffected by a Pre-empt and Clear service action.
The reservation key for the other initiators pre-empted are removed by the Pre-
empt & Clear service action. The reservation key for an initiator that has sent
a Pre-empt & Clear action with its own reservation key specified in the service
action’s reservation key remains unchanged, although all other specified clear-
ing actions, releasing actions, and reservation actions are performed.
Persistent reservations are not superseded by a new persistent reservation from
any initiator except via execution of a PERSISTENT RESERVATION OUT that
specifies either the Pre-empt or Pre-empt & Clear service action. New persistent
reservations not in conflict with an existing persistent reservation execute nor-
mally. The persistent reservation of a logical unit or extent that has the same
Type value is permitted as long as no conflicting persistent reservations other
than the reservations being pre-empted are permitted.