Database access system having time-out mechanism

Details Database access system having time-out mechanism Database access system having time-out mechanism

1999-03-24

2002-04-16

Alam, Hosain T. (Department: 2172)

Data processing: database and file management or data structures

Database design

Data structure types

C707S793000, C707S793000, C714S001000

Reexamination Certificate

active

06374243

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a database access system for use in accessing a plurality of distributed databases from a plurality of client terminals; and a computer program product, which contains an application program for the same.
This application is based on patent application No. Hei 10-146371, filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
FIG. 5
is a block diagram, showing a structure of a conventional database access system. The database access system in this diagram exhibits a three-layer structure, comprising a client layer, an intermediate layer, and a database layer.
In the client layer shown in
FIG. 5
, client terminals (computers)
30
1
-
30
3
installed at the client site are respectively connected to a network
3
. The network
3
can be, for example, an internet. Furthermore, each of the client application programs
31
1-31
3
executed by the respective client terminal
30
1-30
3
is recorded into the memory portion of each respective client terminal
30
1
-
30
3
.
These client application programs
31
1
-
31
3
are programs for requesting a service with regard to an application server
34
, described hereinafter, and for receiving the results of said service.
In addition, in the database layer, the database servers
32
1
-
32
3
are computers which store the databases
33
1
-
33
3
, delivered via the network
3
. Each respective database
33
1
-
33
3
is recorded into the memory portion of the corresponding database server
32
1
-
32
3
. These databases
33
1
-
33
3
are all identical in type.
Furthermore, in the intermediate layer, the application server
34
is a computer which accommodates the client terminals
30
1
-
30
3
via the network
3
, and is connected to the database servers
32
1
-
32
3
. The application server
34
processes service requests from each of the client terminals
30
1
-
30
3
. Additionally, the server application program
35
, run by the application server
34
, is stored into a memory portion of the application server
34
.
The server application program
35
is a program for performing the above-mentioned services, an example of which includes accessing the databases
33
1
-
33
3
, described later. In other words, the application server
34
accesses the databases
33
1
-
33
3
, based on a service request from a client terminal
30
1
-
30
3
, and performs transactions such as updating and reading data, etc. Herein, data update is performed by means of a two-phase commit, comprising the two phases of temporary updating and permanent updating.
In the application server
34
, the transaction processing (TP) monitor
36
performs distributed transaction processing, or more concretely, accesses the databases
33
1
-
33
3
. Hereinafter, distributed transaction processing represents the process of accessing the distributed databases
33
1
-
33
3
.
Herein, the distributed transaction standard employs a TX/XA interface using X/Open.
FIG. 6
is a block diagram, showing a reference model of the above-mentioned distributed transaction processing; and
FIG. 7
is a block diagram, showing a TX/XA interface using X/Open. In
FIGS. 6 and 7
, the corresponding parts to
FIG. 5
have the same reference numbers.
In
FIG. 6
, the transaction manager
37
corresponds to the transaction processing monitor
36
shown in
FIG. 5
, and possesses an interface with the server application program
35
.
The resource mangers
38
1
-
38
3
are, individually, managed by the server application program
35
and the transaction manager
37
, and correspond, respectively, to the databases
33
1
-
33
3
shown in FIG.
5
. Herein, the resource managers
38
1
-
38
3
interface with both the transaction manager
37
and the server application program
35
.
In addition, in
FIG. 7
, the resource manager
38
1
, (see
FIG. 6
) is a general term for the database
33
1
, (see
FIG. 5
) and the communication resource manager
39
1
. The communication resource manager
39
1
controls communication between other systems (not shown) and the database server
32
1
, via the network
44
. Herein,
FIG. 7
shows only a structure of the resource manager
38
1
, shown in
FIG. 6
; however, structures of the resource managers
38
2
and
38
3
, shown in
FIG. 6
, are identical to the structure of the resource manager
38
1
, shown in FIG.
7
.
The TX interface
40
is an interface between the server application program
35
and the transaction manager
37
. The XA interface
41
is an interface between the transaction manager
37
and the database
33
1
. The XA+interface
42
is an interface between the transaction manager
37
and the communication resource manager
39
1
. The application/resource manager interface
43
is an interface between the server application program
35
and the database
33
1
.
As described above, a conventional database access system possesses four interfaces: the TX interface
40
; the XA interface
41
; the XA+interface
42
; and the application/resource manager interface
43
. Further, the database
33
1
, is accessed by each of the server application program
35
and the transaction manager
37
, via another interfaces such as the XA interface
41
and the application/resource interface
43
, respectively.
In the following, the operation of the above-mentioned conventional database access system is described.
In the descriptions below, an example case in which a client terminal
30
1
, shown in
FIG. 5
, requests the application server
34
for a service, such that the application server
34
updates the databases
33
1
, and
33
2
, in order to respond to the service request.
In
FIG. 5
, when service request data is inputted from the client terminal
30
1
, to the application server
34
via the network
3
, the application server
34
performs the following processing by means of running the server application program
35
.
That is, the application server
34
accesses the database servers
32
1
, and
32
2
, in order to temporarily update the databases
33
1
, and
33
2
. Concretely, the server application program
35
(i.e., the application server
34
) provides the command for temporarily updating the database to the transaction manager
37
via the TX interface
40
. As a result, the transaction manager
37
temporary updating of the above-mentioned data, by means of accessing the databases
33
1
, and
33
2
via the XA interface
41
.
Subsequently, after this temporary updating is completed, under normal circumstances, the server application program
35
(i.e., the application server
34
) outputs the control data for performing permanent updating of the databases
33
1
, and
33
2
, to the transaction manager
37
via the TX interface
40
. Accordingly, the transaction manager
37
performs permanent updating of the data, by means of accessing the databases
33
1
and
33
2
via the XA interface
41
.
A conventional database access system is designed to access a plurality of the databases
33
1
-
33
3
in parallel, by means of a single transaction manager
37
(i.e., transaction processing monitor
36
). This causes in an extremely complex structure for both the transaction manager
37
(i.e., transaction processing monitor
36
) and the TX interface
40
.
Additionally, a conventional database access system is designed to have four interfaces: the TX interface
40
; the XA interface
41
; the XA+interface
42
; and the application/resource manager interface
43
, shown in
FIG. 7
, which results in a large number of interfaces.
In summary, a conventional database access system is disadvantageous from the viewpoint of its high costs secondary to the above-mentioned complex structure and large number of interfaces.
Moreover, a conventional database access system accesses a plurality of the databases
33
1
-
33
3
by means of a single transaction manager
37
(i.e., the transaction processing monitor
36
). Accordingly, it is absolutely necessary for the databases
33
1
-
33
3
to be identical in type.
Thus, c

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