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The host computer can reserve any logical unit that has been reserved by the
same host computer.
Once a reservation is established, if another host computer issues a command
other than the INQUIRY, REQUEST SENSE or RELEASE command to the
reserved logical unit, that command is rejected with the RESERVATION
CONFLICT status set.
(2) Third party reservation
The third-party reservation feature of the RESERVE command allows the host
computer to reserve a logical unit for another specified SCSI device. This
feature is applicable to multi-host systems that use the COPY command. (The
COPY command proper is executed by another SCSI controller. )
Third party reservation is disabled when the 3rdPty (Third Party) bit is set to 0.
In this case, the controller ignores the Third Party Device ID field.
When the 3rdPty bit is set to 1, the controller reserves the logical unit for
another SCSI device specified in the Third Party Device ID field.
The Third Party Device ID field contains the SCSI ID for another SCSI device
to be reserved as the logical unit.
Third Party reservation processing proceeds in the same way as in logical unit
reservation except that it allows another SCSI device to reserve the logical unit.
This SCSI controller releases a third party reservation when it receives a valid
RESERVE command from the same host computer (superseding reservation),
when it receives a third party Release command specifying the same third party
device ID, when it receives a BUS DEVICE RESET message from any host
computer, or when a hardware reset condition occurs.
(3) Superseding reservation
The host computer that retains a logical unit reservation can change the
reservation status by issuing another RESERVE command. This superseding
RESERVE command releases the old reservation state when the new
reservation request is allowed. If the new reservation request is not accepted,
the old reservation state is preserved. If the superseding reservation conflicts
with the preceding active reservation state (other than
the reservation being superseded), the controller rejects this command with the
RESERVATION CONFLICT status.
The primary purpose of superseding reservation is to change the SCSI device
ID in the third party reservation state.
This feature is made available for the COPY command that is used between
different SCSI devices.
RESERVE:(16h)
5 COMMAND DESCRIPTIONS
OEM MANUAL:K6602924
Revision: 1 / Date: 2003.03.06
Page: 225 / 273
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