User's Guide

Chapter 2 Media Changer Commands
Persistent Reserve Out Command (5Fh)
Quantum SuperLoader 3 Software Interface Guide 78
Persistent Reserve Out Command (5Fh)
The PERSISTENT RESERVE OUT command is a 10-byte command used to
reserve a logical unit for the exclusive or shared use by an initiator. The
command is used in conjunction with the
PERSISTENT RESERVE IN
command; it is not used with the
RESERVE and RELEASE commands.
Persistent reservations conflict with reservations made via the
RESERVE
command. Initiators that perform
PERSISTENT RESERVE OUT actions are
identified by a reservation key assigned by the application client. The
client may use the
PERSISTENT RESERVE IN command to identify which
other initiators within a system hold conflicting or invalid persistent
reservations and use the
PERSISTENT RESERVE OUT command to
preempt those reservations if necessary.
Note that since persistent reservations are not reset by the
TARGET RESET
task management function or other global actions, they can be used to
enact device sharing among multiple initiators. The
PERSISTENT
RESERVE OUT
and PERSISTENT RESERVE IN commands provide the
means for resolving contentions in multiple-initiator systems with
multiple port target. By using the reservation key to identify persistent
reservations, it is possible to determine which ports hold conflicting
persistent reservations and to take over such reservations from failing or
“greedy” initiators.
The following figure illustrates the format of the
PERSISTENT RESERVE
OUT
command; the table that follows explains the data fields of the
command.
Note: Support for Persistent Reserve is drive type dependent. See
individual drive documentation for complete details.