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Chapter 3 Media Changer Commands

Persistent Reserve Out Command (5Fh)

Quantum ATL SuperLoader Software Interface Guide 109

05h Pre-empt

& Clear

A PERSISTENT RESERVE 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 RESERVE 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 RESERVE 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 RESERVE 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.

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Persistent reservations are not superseded by a new persistent reservation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 RESERVE 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.

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