User's Guide

Chapter 2 Emulated Medium Changer SCSI Commands
Reserve (16h)
Quantum DX-Series Software Interface Guide 95
Reserve (16h) 2
This command reserves the specified DX-Series system or elements for
exclusive use by the requesting initiator or another specified SCSI device.
The reservation remains in effect until one of these conditions is met:
• The initiator that made the reservation sends a valid Reserve
command (see
table 62) capable of overriding the reservation
• Element reservations replace all previous element reservations
with the same Reservation ID from the same initiator, and
cannot override Unit reservations
• Unit reservation can override any previous reservation from the
same initiator, regardless of Reservation ID
• The DX-Series system or element is released by a valid Release
command from the same initiator
•A Bus Device Reset message is received from any initiator.
• A hard reset occurs
The occurrence of the last two conditions is indicated by the DX-Series
system returning a check condition status with a sense key of Unit
Attention on the next command following the condition. It is not an error
to issue a Reserve Unit command to a DX-Series system that is currently
reserved to the requesting initiator.
• The target returns a Reservation Conflict status if a Unit Reserve
command is:
• Attempted on a unit that has been reserved by another initiator
• Contains any element previously reserved by another initiator
• The target returns a Reservation Conflict status if an Element
Reserve command is:
• Issued to an element previously reserved by another initiator
• Contained in a unit that was reserved by any initiator
• Issued to an element reserved using a different Reservation ID
If, after honoring a Unit Reservation, any other initiator attempts to
perform any command except Inquiry, Request Sense, or Release, the
command is rejected with a Reservation Conflict status. A Release
command issued by another initiator is ignored by that reserved logical