OEM MANUAL:K6602771
6 COMMAND DESCRIPTIONS
Revision: 2 / Date: 2002.12.19
Page: 256 / 313
6.24 RESERVE:(16
H
)
Bit
Byte
7
6
5
4
3
2
1
0
0
Operation Code (16
H
)
0
0
0
1
0
1
1
0
1
Logical Unit Number
3rdPty
Third Party Device ID
Extent
0
2
Reservation Identification
3
Extent List Length (MSB)
4
Extent List Length (LSB)
5
Vendor Unique
Reserved
Flag
Link
0
0
0
0
0
0
The RESERVE command reserves a logical unit for the host computer issuing this
command. The third-party reservation feature allows the logical unit to be reserved
for another specified SCSI device.
The RESERVE and RELEASE commands provide the basic mechanism for resolving
contentions that can occur in multi-host (initiator) systems.
Since this SCSI controller does not support the extended reservation feature, the
Extent bit must always be set to 0. If this is not observed, the controller creates the
CHECK CONDITION status with ILLEGAL REQUEST sense key.
The controller is considered as support of only the RESERVE (10) command in order
to specify Third Party Device ID by AL_PA to third party reserve.
The controller ignores the Reservation Identification and Extent List Length fields
that are used by the extent reservation feature. Accordingly, no Data Out phase can
occur.
(1) Logical unit reservation
The RESERVE command requests the controller to reserve the specified logical
unit so that the host computer can use the entire logical unit exclusively until
the reservation is superseded by another valid RESERVE command issued by
the same host computer or until the reservation is released by a RELEASE
command from the same host computer, by a Bus Device Reset message from
another host computer, or by a hardware reset.
A logical unit reservation is rejected with the RESERVATION CONFLICT
status set if the specified logical unit has already been reserved by another host
computer. In this case, the reservation request is not queued into the
controller (the RESERVE command itself is queued, however).
RESERVE:(16h)