Quantum 10K II - Manual (Page 196)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–129
PERSISTENT RESERVATION OUT Command (5Fh) (continued)
Table 5–59 PERSISTENT RESERVATION OUT Command’s Service Action
Descriptions (continued)
Code Name Description
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 registered 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 being 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
RESERVATIONS PREEMPTED. Commands that follow, and retries of
commands that timed out because there were cleared 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 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 clearing 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Persistent reservations are not superseded by a new persistent reservation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 normally. 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.