Quantum 10K II - Manual (Page 258)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–191
5.35 RESERVE (6) Command (16h)
The RESERVE and the RELEASE commands are used for contention resolution in
multiple-initiator systems. The RESERVE command is used to reserve a logical unit.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (16h)
1 Reserved 3rdPty Third Party Device ID Extent
2 Reservation Identification
3 - 4 Extent List Length
5 Control
Figure 5–89 RESERVE (6) Command Descriptor Block — Data Format
Table 5–91 RESERVE (6) Command — Field Descriptions
Field Description
3rd Pty When set to 1, it indicates that the Third Party Device ID field is valid.
Third Party Device ID Required and used only when the 3rdPty bit is set, in which case this
field specifies the SCSI ID (0 through 7 only) of the initiator to be
granted the reservation of the logical unit. The drive preserves the
reservation until one of the following occurs:
• It is superseded by another valid RESERVE command from the
initiator.
• It is released by the same initiator.
• It is released by a TARGET RESET message from any initiator.
• It is released by a hard reset condition.
The drive ignores any attempt to release the reservation made by any
other initiator. For example, if ID7 sends ID2 a Third Party reservation
on behalf of ID6 (the target at ID2 gets reserved for the initiator ID6),
then only ID7 can release the target at ID2 (using a Third Party release).
ID6 cannot release the reservation even though the reservation was
made on its behalf.
(continued)