JPH10161922A - Replica type definition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily designate the range for copying a part of database on the primary side to the replica side in a type unit, to accelerate the judgement of conditions at that time and to attain the maintenance of consistency of database by utilizing the modification hierarchy of type in an object oriented database. SOLUTION: A database managing system to be applied to this system has type definition copy steps 102 (102a and 102b), instance preparation possibility information 106 and instance preparation possibility discrimination step 111 and performs control so as to disable that instance preparation by copying a supertype simultaneously at the time of type definition copy. Besides, a subtype selection/instance preparation step 112 is provided and when the subtype selection of that type is enabled, any one subtype is selected so that the instance of that selected subtype can be prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a non-shared type distributed object-oriented database management system having a database duplication function, in which only a part of a database is duplicated or data can be updated / added at a destination. The present invention relates to a replica type definition method which is particularly effective when it is necessary to simply specify whether or not the replica type is specified.

[0002]

2. Description of the Related Art In the case of a relational database, the specification of a replication range in database replication is described in the document "Replication Mechanism and Application for Realizing Distributed Database, Nikkei Computer 1995.7.10, pp. 127-
Nikkei Open Systems 1995.9, n, which is going to expand additional functions than RDBMS DB engine for PC server and 131
o.30, pp. 311-321 ", etc., a subset of the table is performed using conditional clauses.

[0003] The replication of an object-oriented database is described in Yuh-MingShyy, etc., VERSAN.
T Replication: Supporting Fault-Tolerant Object Da
tabases, SIGMOD Record Vol.24, No. 1, 1995, pp.441
-442 ", this conventional technique replicates all the contents of the database, and does not allow the designation of a replication range.

[0004]

In the former method of the prior art described above, in the case of a relational database, it is necessary to specify a conditional phrase for specifying a duplication range. Need to be evaluated. On the replica side, it is necessary to evaluate the conditions in order to prohibit the creation of instances that do not satisfy the replication range conditions. If the table itself is a plurality of tables in order to divide the duplication range, the user or the application must process them consciously as different tables. Further, in the latter method of the prior art for an object-oriented database, since the entire database is duplicated, the duplication range cannot be specified.

[0005] In an object-oriented database, instances having the same type are grouped based on the concept of a type. There is an inheritance relationship between types, and when there is a reference type and a subtype inheriting the type (the reference type is called a supertype from the viewpoint of the subtype), the instance of the subtype is also included. It is characterized in that it can be searched, referenced, and updated (excluding generation) as an instance of the reference type. The present invention has been devised in view of this feature.

A first object of the present invention is to specify a replication range in an object-oriented database in units of a type using the inheritance of the types, thereby selecting an instance to be replicated on the primary side and replicating. It is an object of the present invention to provide a replica type definition method that can speed up the determination of whether an instance can be created on the side and that enables a user or an application to search, refer to, and update an instance without being aware of the actual type difference.

A second object of the present invention is to provide, in addition to the above object, a replica which does not need to be aware of the type difference between a type accessed by a user or an application and a subtype capable of generating an instance when generating a replica-side instance. It is to provide a type definition method.

[0008]

The above object is achieved by the following invention. In other words, in order to achieve the first object, it has a type duplication step, instance creation availability information, and an instance creation availability determination step, and when a replica type replication request is made to the database management system on the primary site side, the A replica type replication method is also provided in which the super type is simultaneously replicated in the database of the replica site, and the creation of an instance of the simultaneously replicated super type is prohibited.

In order to achieve the second object, in response to an instance creation request of a type that cannot create an instance at a replica site, one subtype that generates an instance of the subtype of the replication type is selected, A replica type definition method having an instance access step including a subtype selection and instance creation step for generating an instance of the selected subtype is provided.

An operation for achieving the first object will be described. When the duplication range is specified by type, the type duplication step copies the supertype of the type from the database at the primary site to the database at the replica site in addition to the instance of the specified type and the type. In the database of the replica site, generation of instances of the super type that are simultaneously duplicated by the instance access step is prohibited, and as a result, instances other than the type specified as the duplication range are not duplicated / generated. Also, at the time of instance access (excluding generation), by accessing an instance of the supertype through the supertype using the object-oriented abstraction, there is no need to write a program in consideration of the type difference. As a result, the object to be copied can be selected only by determining the type of the object, and the selection of the object to be copied can be speeded up. At the same time, on the replica side, an object that does not satisfy the condition can be determined only by referring to the type, so that the processing can be speeded up.

In order to achieve the second object, in the subtype selection / instance creation step, one subtype of the type for which an instance creation request has been issued is selected, and its instance is created and accessed (excluding creation). At this time, by accessing the generated instance through the type for which the instance creation request has been issued, it is not necessary to be aware of the type difference in instance generation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing a database management system according to the present invention. The primary site database management system 101 includes a type duplication step 102a for transferring definition information of the primary type 105a managed by the primary site database 103 to the replica site database management system 108 via a network. Based on the transferred definition information, the database management system 108 at the replica site performs a type replication step 102b for defining the replica type 105b in the database 114, and an instance access step 110 for accessing an instance of the defined replica type. Is included. The type 105 includes instance creation possibility information 106, and the instance access step 110 refers to the instance creation possibility information 106 to determine whether an instance can be created. Subtype selection / instance creation step of selecting one subtype of the type and creating the instance when an instance creation request is issued
112 is included.

Next, an algorithm according to an embodiment of the present invention will be described.

FIG. 2 shows an algorithm in the type definition duplication step 102. When a user requests a duplication range specification by type specification, in the type definition duplication step 102a on the definition transfer side, the definition information of the supertype of the type specified by the user is obtained (step 201), and then the duplication specification type Acquire definition information (step 202),
The type definition information acquired in step 203 and the instance of the type designated for duplication are sequentially transferred from the super type definition information to the type definition duplication step 102b on the definition receiving side. In the type definition duplication step 102b on the definition receiving side, the processing from step 204a to step 204b is repeated from the supertype side for the transferred type definition. First, it is determined whether or not the transferred type definition exists (step 205), and if not, a type definition is created (step 206). Next, it is determined whether or not the created type is the copy designation type (the type transfer information transferred last is the copy designation type) (step 207). The value of the generation permission / inhibition information 106 is set to "permitted" (step 208). Otherwise, the value of the instance generation permission / inhibition information 106 in the created type definition is set to "not permitted".
(Step 209). Finally, in the instance creation step 210, an instance of the type designated for duplication (excluding the supertype duplicated at the same time) is created.

FIG. 3 shows an algorithm in the instance access step 110 according to the second embodiment of the present invention, which is started when a user requests to create a certain type of instance. First, it is determined whether or not an instance of the type can be created with reference to the instance creation availability information 106 of the type definition 105 for which the user has requested the instance creation (step 111). 301).

FIG. 4 shows an algorithm in the instance access step 110 in the third embodiment of the present invention. The instance creation availability determination step 111 and the instance creation step 301 are the same as those in FIG.
If the instance creation information is “No”, the process of steps 401a to 401b is repeated for each subtype. First, it is determined whether an instance can be created for each subtype with reference to the instance creation availability information 106 (step 402). If an instance can be created, create an instance of the subtype (step 4
03), end the processing. If an instance cannot be created, the same process is repeated for the next subtype.

Hereinafter, a first embodiment relating to duplication of types and instances when a duplication range is specified by type specification will be described with reference to FIG. When the range to be replicated in the database 114 of the replica site is designated as the type “company”, the type “company” 105a which is a super type of the type “company” designated as the replication range in step 201 of the type replication step 102a It acquires the definition information of the type “company” 105c whose definition information has been set as the duplication range in step 202, and transfers them and the instance 502a to the type duplication step 102b.

The type duplication step 102b first determines whether the type (type "company") is already defined on the replica site side (step 205). In this case, since it is not defined, the type "company" 105b is defined (step 206). Next, it is determined whether this type is the type designated as the duplication range (step 2).
07), since this type is not the type specified as the duplication range, the value of the instance
(Described as x in the figure) (step 208). At this time, it should be noted that the value of the instance creation availability information 106a of the primary type 105a of the type 105b is “OK” (described as “O” in the figure). Next, type "stock"
In this case, since the type is designated as the duplication range, the result is Y in step 207, so the value of the instance creation permission / inhibition information of the type 105d is set to “permitted” (in the figure, ○). . Finally, the instance 502a
Duplicate as 502b.

Next, a second embodiment of instance generation will be described with reference to FIG. In the instance access step 110 used in the present embodiment, FIG.
Algorithm is used. When a request to create an instance of the replica database type "company" 105b is issued, the instance access step 110 of the replica database management system 108 first creates an instance by referring to the value of the instance creation availability information 106b of the type 105b. It is determined whether or not is possible (step 111). In this case, creation of the instance 601 can be prohibited because the value of the instance creation availability information is “No”.

Next, a third embodiment of instance generation will be described with reference to FIG. In the instance access step 110 used in this embodiment, the algorithm shown in FIG. 4 is used. When a request to create an instance of the replica database type "company" 105b is issued, the instance access step 110 of the replica database management system 108 first creates an instance by referring to the value of the instance creation availability information 106b of the type 105b. It is determined whether or not is possible (step 111). In this case, since the value of the instance creation availability information is “No”, the subtype of the type 105b (in this example, the type “stock” 1
Regarding 05d), it is determined whether an instance can be generated (step 402). In this case, the value of the instance creation permission / prohibition information 106d is “possible” (○ in the figure), and thus an instance 701 of type “stock company” is generated.

Next, an embodiment relating to instance access will be described with reference to FIG. When an application or a user accesses the type of the database 103 of the primary site and the database 114 of the replica site, it accesses the instance of the subtype through the type "company" (105a, 105b). Provided by the system). As a result, even if the duplication range is specified for each type, it is possible to handle the types uniformly in the database 103 of the primary site without being aware of the type difference.

[0023]

As described above, according to the present invention, the range of copying a part of the database on the primary side to the replica side in the object-oriented database using the type inheritance hierarchy can be easily specified in units of type. In addition, means for speeding up the condition determination at that time and maintaining the consistency and consistency of the database are provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a system.

FIG. 2 is an algorithm used in a type definition duplication step.

FIG. 3 is an instance creation algorithm used in the second embodiment of the present invention.

FIG. 4 is an instance creation algorithm used in a third embodiment of the present invention.

FIG. 5 is an example of a type definition in the first embodiment of the present invention.

FIG. 6 is an example of a type definition in a second embodiment of the present invention.

FIG. 7 is an example of a type definition in a third embodiment of the present invention.

[Explanation of symbols]

101 ... first database management system, 102a ... first type definition duplication step, 102b ... second type definition duplication step, 103 ... first database, 105a ... first type definition, 105b ... second type Definition: 106: instance creation availability information; 108: second database management system; 110: instance access step; 111: instance creation availability determination step; 112: original subtype selection / instance creation step; 114: second database.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiko Kuroi 5030 Totsukacho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Software Development Division, Hitachi, Ltd.

Claims (4)

[Claims] An object-oriented database is stored at a primary site, and in a non-shared type distributed object-oriented database management system having a function of replicating the database to a replica site, a range of replication is specified by type, and the replication is performed. When the type specified as the range has one or more supertypes, a type replication step of replicating the supertype of the type from the database at the primary site to the database at the replica site in addition to the type and the instance of the type. A replica method of a database characterized by including. 2. The non-shared type distributed object-oriented database management system according to claim 1, further comprising: an instance access step of controlling not to generate an instance of said duplicated super type at a replica site. Replica method. 3. The non-shared type distributed object-oriented database management system according to claim 2, wherein the type definition data includes instance generation availability information for distinguishing whether generation of an instance of the type is possible at a replica site, In the instance access step,
Determining whether the instance can be created by referring to the availability information. 4. The non-shared type distributed object-oriented database management system according to claim 1, wherein a type in which the value of the generation permission / prohibition information is not instantiable is defined, and the duplication type includes one or more subtypes. Have,
If there is means for selecting one subtype from them, select one of the subtypes and select a subtype to generate an instance of the selected subtype.
An instance creation step.
The replica type definition method according to claim 1.