ACL 4/52 Software Interface Guide
Document 6211225-03
Version 3.0
SCSI Interface
3-55
Reserve (16h)
Reserve reserves the specified library or elements for exclusive use by
the requesting initiator or the another specified SCSI device. The
reservation remains in effect until one of the following conditions is
met:
•
The initiator that made the reservation sends a valid Reserve
command capable of overriding the reservation. Element
reservations will replace all previous element reservations with the
same Reservation ID from the same initiator, and can not override
Unit reservations. Unit reservation can override any previous
reservation from the same initiator, regardless of Reservation ID.
•
The library 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 library
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 Reserve Unit to a library that is currently reserved to the
requesting initiator.
If a Unit Reserve is attempted on a unit that has previously been
reserved by another initiator or contains any element previously
reserved by another initiator, the target returns a Reservation Conflict
status. If an Element Reserve is attempted on an element previously
reserved from another initiator or contained by a unit previously
reserved by any initiator or previously element reserved with a
different Reservation ID, the target returns a Reservation Conflict
status.
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 unit. If, after honoring an Element Reservation, any other
initiator issues a command other than Release to that element, the
command is rejected with a Reservation Conflict status. A Release
command issued by another initiator is ignored by the reserved
element.
