Redundant apparatus

Details Redundant apparatus Redundant apparatus

1998-05-08

2001-02-20

Iqbal, Nadeem (Department: 2785)

Error detection/correction and fault detection/recovery

Data processing system error or fault handling

Reliability and availability

C714S025000

Reexamination Certificate

active

06192485

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a redundant apparatus, and in particular to a redundant apparatus which is formed of an active unit and a stand-by unit to which the active unit is switched over when a fault has occurred in the active unit.
In recent years, an information processing system has been made large-sized and complicated increasingly. Especially in a system which works on-line i.e. in real time, a fault partially generated may influence on the whole system to cause a big damage.
To deal with such a fault, there are the art of redundancy to cover the influence of the fault, the art of diagnosing and repairing the fault, and the art in which the former two arts are combined. Among these arts, the art of redundancy is utilized in a redundant apparatus which switches an active unit over to a stand-by unit when a fault has occurred, and diagnoses and repairs the fault to shorten an unavailable time of the system.
In such a redundant apparatus, it has become more and more important to have a restoration speed by which the system has no influence of a fault, and to have an effect for the cost.
2. Description of the Related Art
FIG. 17
shows an arrangement of an electronic switchboard known as the prior art of a redundant apparatus. This apparatus is formed of a circuit equipment DTSH connected to a subscriber
1
and a subscriber
2
, and an upper unit
100
connected to this circuit equipment DTSH with a control signal circuit C and main signal circuits A
0
-A
2
. The upper unit
100
is formed of a controller
110
connected to the control signal circuit C, a switch portion
120
connected to the main signal circuits A
0
-A
2
and the controller
110
, and a diagnosis portion
212
connected to the switch portion
120
.
The circuit equipment DTSH is formed of a switch-over portion
300
connected to the subscribers
1
and
2
, circuit corresponding equipments (abbreviated as CCE) DT
0
-DT
2
connected to the switch-over portion
300
with the main signal circuits A
6
-A
8
respectively, and a circuit controller DTC which is connected to the circuit corresponding equipments DT
0
-DT
2
with main signal circuits A
3
-A
5
respectively and also connected to the control signal circuit C and the main signal circuits A
0
-A
2
.
It is to be noted that the main signal circuits A
0
, A
3
, and A
6
, the main signal circuits A
1
, A
4
, and A
7
, and the main signal circuits A
3
, A
5
, and A
8
are the same as the main signal circuits A
0
, A
1
, and A
2
, respectively. Therefore, in the following descriptions the main signal circuits A
0
, A
1
, and A
2
represent the other main signal circuits. Moreover, the main signal circuits A
0
, A
1
, and A
2
which connect the circuit controller DTC to the switch portion
120
can be one logical circuit as a high way.
In a normal operation, the circuit corresponding equipments DT
0
, DT
1
are preset as an active unit. By the switch-over portion
300
, the circuit corresponding equipments DT
0
and DT
1
are connected to the subscribers
1
and
2
, respectively. The circuit corresponding equipment DT
2
is preset as a stand-by unit, and is not connected to either of the subscribers
1
or
2
. Namely, the equipment DT
2
is a stand-by circuit corresponding equipment.
As shown in
FIG. 17
, the subscriber
1
and the switch portion
120
are fixedly connected with the main signal circuit A
0
through the switch-over portion
300
, the circuit corresponding equipment DT
0
, and the circuit controller DTC. In the same way, the subscriber
2
and the switch portion
120
are fixedly connected with the main signal circuit A
1
through the switch-over portion
300
, the circuit corresponding equipment DT
1
, and the circuit controller DTC.
The diagnosis portion
212
sends to the stand-by circuit corresponding equipment DT
2
a test signal on the main signal circuit A
2
through the switch portion
120
and the circuit controller DTC under the control of the controller
110
, thereby diagnosing from the response signal whether or not the circuit corresponding equipment DT
2
is normal.
FIG. 18
shows an operation example in the case where a fault has occurred in the circuit corresponding equipment DT
0
shown in FIG.
17
. Having received a notification that the fault has occurred in the circuit corresponding equipment DT
0
from the circuit controller DTC, the controller
110
makes the switch-over portion
300
separate the circuit corresponding equipment DT
0
from the subscriber
1
in order to withdraw the circuit corresponding equipment DT
0
from its active state.
After having instructed the switch portion
120
to set again a passage from the main signal circuit A
0
to the main signal circuit A
2
, the controller
110
makes the switch-over portion
300
connect the stand-by circuit corresponding equipment DT
2
to the subscriber
1
for the continuous operation.
Namely, different from
FIG. 17
, the subscriber
1
will be connected to the main signal circuit A
2
through the switch-over portion
300
, the stand-by circuit corresponding equipment DT
2
, the circuit controller DTC, and the switch portion
120
.
The controller
110
sets again the passage of the switch portion
120
to connect the diagnosis portion
212
and the circuit corresponding equipment DT
0
with the main signal circuit A
0
. After the circuit corresponding equipment DT
0
as faulted is exchanged and repaired, the diagnosis portion
212
sends a test signal to the circuit corresponding equipment DT
0
through the main signal circuit A
0
by the instruction of the controller
110
, thereby diagnosing the circuit corresponding equipment DT
0
from the response signal. The result of this diagnosis is sent to the controller
120
.
Recognizing from this diagnosis result that the circuit corresponding equipment DT
0
has been restored to the normal state, the controller
110
puts the stand-by circuit corresponding equipment DT
2
and the restored circuit corresponding equipment DT
0
back to the stand-by state and the active state, respectively, and controls the switch portion
120
and the switch-over portion
300
back to the same connection as shown in FIG.
17
.
It is to be noted that when the circuit corresponding equipment DT
0
is faulted and the stand-by circuit corresponding equipment DT
2
is active and the circuit corresponding equipment DT
1
is also faulted, the subscriber
2
which is connected to the circuit corresponding equipment DT
1
cannot use any circuit corresponding equipment because there is no stand-by circuit corresponding equipment in the stand-by state which is available.
As a measure for this problem, there is a redundant apparatus provided with the plural stand-by circuit corresponding equipments. The function of the redundant apparatus is the same as the redundant apparatus which has only one stand-by circuit corresponding equipment.
In such a prior art redundant apparatus of N+1 type which is formed of e.g. N active circuit corresponding equipments and a single stand-by circuit corresponding equipment, a diagnosis is done by providing N+1 signal systems corresponding to each circuit corresponding equipment. Namely, the main signal circuits like A
0
-A
2
in
FIG. 17
are always required for all of the circuit corresponding equipments which should be actually equipped. Therefore, in an electronic switchboard, 1/N of the hardware capacity of the switch portion always remains unused.
The diagnosis of the circuit corresponding equipment requires a function of confirming signal transmissions and receptions by an apparatus including a circuit corresponding equipment DTC in order to return the signal. For this function a hardware resource of the switch portion in the electronic switchboard has been used.
Namely, the diagnosis of the circuit corresponding equipment of the redundant apparatus of the N+1 formation requires the capacity of 1/N to be occupied in respect of hardware and transactions to be made concerning other parts than circuit corresponding equipments as subj

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