Quantum 10K II - Manual (Page 261)

SCSI Description
5–194 Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives
RESERVE (10) Command (56h) (continued)
Table 5–92 RESERVE (10) Command — Field Descriptions
Field Description
3rd Pty When set to 1, it indicates that the Third Party Device ID field is valid.
LongID When 0, indicates that the third party device associated with the
reservation release has a number smaller than 255 and the ID value
can be sent within the CDB. If set = 1, indicates that the third party
device ID is greater than 255, the ID value within the CDB is ignored,
and the parameter list length is at least eight.
Third Party Device ID Required and used only when the 3rdPty bit is set, in which case this
field specifies the SCSI ID 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• It is superseded by another valid RESERVE command from the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.
Extent If 0, requests that the entire logical unit be reserved for use only by the
initiator until the request is supplanted by another valid RESERVE
command from the same initiator, or until released via a RELEASE (10)
command from the reserving initiator, a hard reset, or a power on
cycle.
If set = 1, the extent reservation option is implemented. This option
allows an application client in a multitasking environment to have
multiple reservations.
The size of the extent list is defined by the contents of the Parameter
List Length field. The extent list consists of zero or more descriptors.
Each descriptor defines an extent beginning at the specified logical
block address for the specified number of blocks. If the number of
blocks is 0, the extent begins at the specified logical block address and
continues through the last logical block address on the logical unit.
The data format of extent descriptors is shown in Figure 5-91.