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SCSI Commands

Quantum DLT 8000 Tape System 5-145

5.12 PERSISTENT RESERVATION OUT Command (5Fh)

The PERSISTENT RESERVATION OUT command is a 10-byte command used to reserve

a logical unit or an extent within a logical unit for the exclusive or shared use by an

initiator. Note that reservations are not persistent across power cycles. The command is

used in conjunction with the PERSISTENT RESERVATION 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 RESERVATION OUT actions are identified by a

reservation key assigned by the application client. The client may use the PERSISTENT

RESERVATION IN command to identify which other initiators within a system hold

conflicting or invalid persistent reservations and use the PERSISTENT RESERVATION

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 RESERVATION OUT and PERSISTENT

RESERVATION 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 figure that follows illustrates the format of the PERSISTENT RESERVATION OUT

command; the table that follows explains the data fields of the command.

1 2 ... 284 285 286 287 288 289 290 291 292 293 294 ... 407 408

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Quantum DLT 8000 Manual Pagina 289