Dell PowerVault TL4000 - Manual (Page 96)

RESERVE 10 (56h)
The RESERVE and RELEASE commands provide the mechanism for contention resolution in multiple
initiator systems. The third-party reservation allows logical units to be reserved for another specified SCSI
device. When a initiator reserves the library, only INQUIRY, LOG SENSE, RELEASE, REQUEST SENSE,
REPORT LUNS, READ ELEMENT STATUS with CurData set and ALLOW MEDIUM REMOVAL
commands are accepted from other initiators. All other commands result in a Reservation Conflict status.
Bit 7 6 5 4 3 2 1 0
Byte
0 Operation Code (56h)
1 LUN 3rdPty Reserved LongID Reserved
2 Obsolete
3 Third-Party Device ID
4 Reserved
5 Reserved
6 Reserved
7 (MSB) Parameter List Length
8 (LSB)
9 Control
Field descriptions:
LongID:
Device IDs greater than 255 are not supported, therefore setting of LongID will result in a Check
Condition status. The Sense Key will be set to ILLEGAL REQUEST and the sense data to
INVALID FIELD IN CDB.
3rdPty:
If the third party (3rdPty) bit is zero, then a third-party reservation is not requested. If the 3rdPty bit
is zero then the LongID and Parameter List Length field shall be ignored. If the 3rdPty bit is one
then the library is reserved by the initiator ID specified in the Third-Party Device ID field. The
reservation is preserved until it is superseded by another valid RESERVE command from the
initiator that made the reservation or until it is released by the same initiator, by a SCSI RESET
message, or by a Hard Reset condition, or by a power-on cycle. The library shall ignore any
attempt to release the reservation made by any other initiator.
Third-Party Device ID:
This field provides the Device ID for the third party when 3rdPty bit is set.
3-82 TL2000 and TL4000 SCSI Reference