User Manual

SCSI Commands Reference Manual, Rev. J 116
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
3.13.2 READ KEYS service action
The READ KEYS service action requests that the device server return a parameter list containing a header and a list of each currently registered
I_T nexus’ reservation key. If multiple I_T nexuses have registered with the same key, then that key value shall be listed multiple times, once for
each such registration.
For more information on READ KEYS see SPC-5.
The format for the parameter data provided in response to a PERSISTENT RESERVE IN command with the READ KEYS service
action is shown in table 78.
PRGENERATION (Persistent Reservations Generation) field
The Persistent Reservations Generation (PRGENERATION) field shall contain a 32-bit counter maintained by the device server that shall be incre-
mented every time a PERSISTENT RESERVE OUT command requests a REGISTER service action, a REGISTER AND IGNORE EXISTING KEY service
action, a REGISTER AND MOVE service action, a CLEAR service action, a PREEMPT service action, or a PREEMPT AND ABORT service action. The
counter shall not be incremented by a PERSISTENT RESERVE IN command, by a PERSISTENT RESERVE OUT command that performs a RESERVE
or RELEASE service action, or by a PERSISTENT RESERVE OUT command that is terminated due to an error or reservation conflict. Regardless of
the APTPL bit value the PRGENERATION value shall be set to zero by a power on.
ADDITIONAL LENGTH field
The ADDITIONAL LENGTH field contains a count of the number of bytes in the Reservation key list. The relationship between the ADDITIONAL
LENGTH field and the CDB ALLOCATION LENGTH field is defined in
2.2.6.
The reservation key list contains the 8-byte reservation keys for all I_T nexuses that have been registered (see SPC-5).
Table 78 PERSISTENT RESERVE IN parameter data for READ KEYS
Bit
Byte
7 6 5 4 3 2 1 0
0
(MSB)
PRGENERATION
. . .
3
(LSB)
4
(MSB)
ADDITIONAL LENGTH (N-7)
. . .
7
(LSB)
Reservation key list
8
(MSB)
Reservation key [first]
. . .
15
(LSB)
n-7
(MSB)
Reservation key [last]
. . .
n
(LSB)