Pioneer SCSI-2 - Manual (Page 142)

Reserve
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2.32 Reserve (16h)
Operation Code is (16h).
3rdPty
Set to one if the initiator requests third-party reservation.
3rd Party Device ID
The SCSI ID of another initiator for which the logical unit shall be reserved.
Ext. (Extent) is not supported. This bit must be 0.
Reservation ID is not supported. This byte must be 00h.
Extent List length is not supported. These bytes must be 00h.
The initiator uses this command to exclusively reserve the specified logical unit. Area
reservations using the Extent bit are not supported. If the 3rd Party bit is 1, the logical unit is
reserved for another SCSI device specified by the 3rd Party Device ID. The initiator can change
the reservation by issuing a new RESERVE UNIT command to the reserved unit. In this case,
the previous reservation is released when the new reservation is received.
The reserved condition is maintained until the original initiator issues another valid RESERVE
UNIT command or a RELEASE UNIT command; when a BUS DEVICE RESET message is
issued by any initiator; or when a hardware reset condition occurs. In the latter two reset cases, a
UNIT ATTENTION condition is reported for the next SCSI command.
Any reservation request by an initiator for a logical unit that has been reserved by another
initiator is rejected, and a RESERVATION CONFLICT status is returned.
If the 3rd Party bit is 1, the logical unit is reserved for the SCSI device indicated by the 3rd-
Party Device ID. The reserved state is maintained as described previously. Any release request
is ignored, and a GOOD status is returned if it comes from an initiator other than the one that
issued the reservation command.