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VI/PER SCSI 60, 125 & 150 THEORY OF OPERA TlON AND MAINTENANCE
5.18 RELEASE UNIT (17h)
The RELEASE UNIT command releases a current Viper drive reservation, if the command is
received from the Initiator that originally established the reservation.
If
the original reserva-
tion was made for a third party, the RELEASE UNIT command Descriptor Block must also
carry the third party data. Any RELEASE UNIT command that arrives from other than the
originating requestor (including one that arrives from the third party currently in command
of the Viper drive) is ignored and Good Status is returned in response to the command.
Additional events and conditions that can cause a reservation to be released are discussed
under the RESERVE UNIT command.
NOTE: It is nDt an error to attempt to release an 10 that is not currently reserved to
the requesting Initiator.
A
reservation cannot be released, if it is reserved by another
Initiator.
5.18.1 RELEASE UNIT Command Descriptor Block
BITS
7
6
5
4
0
BYTe
0
0
0
0
1
1
1
0
0
0
3rd Ply
3rd Party 10
0
~
2
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
0
4
0
0
0
0
0
0
0
0
5
X
X
0
0
0
Flag
Link
,
5.18.2 Command Descriptor Block Field Descriptions
I
~!~~. 1 . ~ · · · · · · · _ ~ - Y _ · - r _ E - S _ ~
__
BI~TS
__
~D~E_S_C_R~I
. . .
P . . . . . .
T . . . . . . . I . .
O_N _____ . . . . . . . . .
~
______
~_I
I
3rd Ply Bil
1
4
The 3rd Party bit is used to
release is for a third-party.
3rd Ply 10
1 to 3
5-44
The 3rd Party 10 specifies an Initiator 10 for
which the release was intended. It is meaningful
only when the 3rdPly bit is set to
1.
Viper drive
does not release a third party reservation if this
field does not identify the Initiator currently in
control of the Viper drive.
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