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While Write Exclusive is active, no other Initiator shall be
permitted WRITE access to the extent.
This reservation shall not
inhibit READ accesses from an Initiator or conflict with a Read
Exclusive reservation
from any Initiator.
This reservation
shall conflict with Write Exclusive,
Exclusive Access,
and Read
Shared reservations which overlap this extent.
While Exclusive Access is active, no other Initiator shall be
permitted any access to the indicated extent.
All Reservation
Types which overlap this extent shall conflict with this reserva-
tion.
While Read Shared is active, no WRITE accesses shall be permitted
by any Initiator to the indicated extent.
This reservation shall
not inhibit READ accesses from any Initiator or conflict with a
Read Shared reservation.
Read Exclusive, Write Exclusive, and
Exclusive Access reservations which overlap with this extent
shall conflict with this reservation.
If the RELATIVE ADDRESS bit (Bit 2 of Byte (0) is 1, the Logical
Block Address shall be treated as a two's complement displace-
ment.
This displacement shall be added to the Block Address last
accessed on the unit to form the Block Address for this extent.
This feature is only available when linking commands and requires
that a previous command in the linked group has accessed a block
of data on the un it;
if not,
the RESERVE Command sha 11 be
rejected with CHECK CONDITION Status and an error code of Bad
Argument (24 H ).
If an Initiator attempts to access (READ or WRITE) a block which
has
been
reserved
and
that
access
is
prohibited
by
the
reservation,
then the operation is not performed and terminates
with RESERVATION CONFLICT Status.
If any access conflict exists,
none of the operation shall be performed.
If any extent in a
unit is reserved in any way, a
FORMAT UNIT Command is rejected
with RESERVATION CONFLICT Status.
Note that
RESERVE commands, whether for a unit or for an extent,
are not queued.
Host software is responsible for queuing reserve
functions,
since careful management of host software is required
to detect and circumvent potential deadlocks.
In multi-host
systems, deadlock prevention may require an auxiliary communica-
tion path or very restrictive programming conventions.
Host software is responsible for monitoring and clearing
reservations generated by attached hosts that have failed with
reservations outstanding.
This may require an auxiliary communi-
cations path.
The reservations for failing hosts may be cleared
using the BUS DEVICE RESET message.
Note that non-failing hosts
must be aware of and provide permission for execution of a BUS
DEVICE RESET since reservations on their behalf will also be
destroyed.
500504-00
6-39
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