JPH03116341A - Dead lock release system - Google Patents

Abstract

PURPOSE:To efficiently release the dead lock by selecting a resource as the processing request object, whose processing right another transaction does not acquire, out of resources as transfer object candidates of a prescribed transaction and transferring this resource to a corresponding transaction. CONSTITUTION:If resources entered in the update right unacquiring resource list of another transaction, for example, a transaction 1n exist in resources entered in the update right transfer resource list stored in an update right transfer resource list storage part 91 of a transaction as the cause of dead lock, for example, a transaction 11, they are added to an update right acquiring resource list storage part 6n corresponding to the transaction 1n. When an update right request resource list storage part 5n and the update right acquiring resource list storage part 6n coincide with each other, the update request of the transaction 1n is executed. Thus, the dead lock is efficiently released because update requests of respective transactions can be successively executed.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a deadlock release method in database management or file input/output management processing of a computer system, and in particular to a deadlock release method in database management or file input/output management processing of a computer system, and in particular, to This invention relates to a deadlock release method for a computer system that accepts processing requests simultaneously.

(Prior Art) Generally, in database management or file input/output management of a computer system, resources in a database or file (for example,
(item, column, record, etc.) is requested to be updated. in this case,
The update processing of each transaction becomes executable when the transaction acquires all update rights for each resource requested for update.

In a system that accepts update requests from multiple transactions at the same time, multiple transactions may request updates to a common resource at the same time. In this case, no transaction will be able to acquire update rights for the resources that are requested to be updated at the same time. As a result, a deadlock situation occurs in which transactions are forever waiting for the transfer of update rights to mutually needed resources.

Conventionally, in order to release such a deadlock state, a process is performed in which some of the transactions causing the deadlock are forcibly sacrificed. In this case, the update request of the victim transaction is not executed, and an error is returned to the application program. The application program that received the error issues a roll pack command or a try command in order to re-execute the update process that was not executed.

In this way, conventionally, in order to release a deadlock state, an application program is used to re-execute an update request, so when a transaction update request is rejected, a roll pack instruction or retry request is It was necessary to design and code the application program. For this reason, the application program has become complicated, and it has been difficult to efficiently release the deadlock state.

(Problem to be Solved by the Invention) Conventionally, in order to release a deadlock state, an error is sent back to the application program, which has the disadvantage that the design of the application program becomes complicated and the deadlock state cannot be released efficiently. was there.

This invention was made in view of the above points, and it is possible to eliminate deadlocks efficiently by executing update requests of each transaction sequentially without sending an error back to the application program. The purpose is to provide a release method.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention provides a deadlock release method for a system that simultaneously accepts processing requests from a plurality of transactions for a database or file. a first storage means for storing rank information allocated in advance; and a second storage means for storing, for each transaction, a resource for which a processing right has been acquired among the resources requested to be processed by each transaction. , a third storage means for storing, for each transaction, resources for which processing rights have not been acquired among the resources requested to be processed by each of the transactions;
, refers to the second and third storage means, and selects, for each transaction, a resource with a higher rank than a predetermined rank of resources for which processing rights have not been acquired, among the resources for which processing rights have been acquired, as transfer target candidates for each transaction. Referring to a transfer candidate selection means for selecting a resource, a fourth storage means for storing the resource of a transfer target candidate selected by the transfer candidate selection means for each transaction, and the third and fourth storage means. transfer means that selects a processing request target resource for which no other transaction has acquired processing rights from among resources that are transfer target candidates for a given transaction, and transfers processing rights for the selected resource to a corresponding transaction; It is characterized by comprising the following.

In this deadlock release method, resources that are candidates for transfer are selected for each transaction, and among the resources that are candidates for transfer, the resource that is the subject of a processing request for which no other transaction has acquired processing rights is transferred to that transaction. be done. Therefore, even if a deadlock occurs, transactions do not have to wait forever for processing rights to mutually needed resources, and the deadlock can be efficiently released.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a system configuration for realizing a deadlock release method according to an embodiment of the present invention.

The plurality of transactions 11 to In each convey an information processing request generated in response to each event in various business processes, and the information processing request includes, for example, updating the resources of the database (or file) 40. There are things such as things and things that take out and refer to their resources. These transactions 11 to 1n are supplied to the database (or file) management section 30.

The database (or file) management unit 30 is for managing input/output to the database (or file) 40, and uses the resource list management unit IO to perform transfer processing for each resource in the database (or file) 40. control etc.

If a deadlock occurs in this system due to simultaneous update requests issued to the resources of the database 40 from transactions 11 to In, the deadlock notification unit 20 detects this and informs that the deadlock has occurred. is notified to the database management unit 30.

The resource list management unit 10, in collaboration with the database management unit 30, stores update request resource list storage units 51 to 5n, update right acquired resource list storage units 61 to Bn, update right unacquired resource list storage units 71 to 70, and resource list storage units 51 to 5n. Ranking list storage section 81. Update right transfer resource list storage units 91 to 9n and comparison unit 11
．． 12.

The update request resource list storage units 51 to 50 respectively correspond to transaction ll=In, and these update request resource list storage units 51 to 50 store a list of all resources that have been requested to be updated by the corresponding transaction. be done.

The update right acquisition resource list storage units 61 to 6n correspond to transactions 11 to In, respectively, and these update right acquisition resource list storage units 61 to 6n contain a list of resources for which the corresponding transaction has acquired update rights. Stored.

The update right unacquired resource list storage units 71 to 7n correspond to transactions 11 to In, respectively, and these update right unacquired resource list storage units 71 to 7n store information about the resources for which update rights have not been acquired for the corresponding transactions. A list is stored. The update right unacquired resource list is obtained by the comparison unit 11 comparing the corresponding update request resource list and update right acquired resource list.

The resource ranking list storage unit 81 stores ranking information assigned in advance to each resource in the database 40. The update right transfer resource list storage units 91 to 9n correspond to transactions 11 to In, respectively, and these update right transfer resource list storage units 91 to 9n include the following:
A list of resources to be transferred to other transactions among the resources for which the corresponding transaction has acquired update rights is stored. The list of resources to be transferred is obtained by the comparison unit 12 by referring to the update rights acquired resource list, the update rights unacquired resource list, and the resource ranking list. In other words, a resource that has been requested to be updated by another transaction among the resources for which the update right has been acquired and that has a higher ranking than the resource that has the lowest ranking among the resources that have not acquired the update right is selected as the resource to be transferred. Ru.

Next, the procedure for deadlock release processing in the system shown in FIG. 1 will be explained with reference to the flowcharts in FIGS. 2(A) to 2(C).

When a deadlock condition is detected by the deadlock notification unit 20, first, as shown in FIG. 2(A), one of the multiple transactions causing the deadlock is selected (step AI
). Next, the update request resource list storage unit 51 and the update right acquisition resource list storage unit 61 corresponding to the selected transaction, for example transaction 11, are referred to, and the comparison unit 11 compares the update right acquisition resource list and the update right acquisition resource list. are compared (step A2).

As a result, an update right unacquired resource list corresponding to the transaction 11 is generated, and it is stored in the update right unacquired resource list storage section 71 (step A3).

Next, the resource ranking list storage section 81 and the update right unacquired resource list storage section 71 are referred to, and the resource with the lowest rank among the update right transfer resources is confirmed (step A4). When the storage unit 61 is referred to,
It is determined whether a resource with a higher rank than the unacquired resource with the lowest rank is stored in the update right acquisition resource list storage unit 61 (step A5). If there is an acquired resource with a higher rank than the unacquired resource with the lowest rank, the acquired resource is selected as the update right transfer resource, and an update right transfer resource list is generated (step AS). This update right transfer resource list is stored in the update right transfer resource list storage section 91.

The process of step At-AS is executed in the same way for each transaction causing the deadlock, and when it is determined that the process for all transactions has been completed (step A7), the process shown in FIG. The process moves to steps A8 to AI2 in (B).

When the processing of steps A1 to A6 is completed for each transaction causing the deadlock, first, as shown in FIG. 2(B), one of the transactions causing the deadlock is one is selected (step A8). Next, it is determined whether or not among the resources on the update right transfer resource list corresponding to the selected transaction, for example transaction 11, there is a resource listed on the update right unacquired resource list of another transaction ( Step A9).

If there is a resource listed in the update right transfer resource list of transaction 11 that is listed in the update right unacquired resource list of another transaction, for example, transaction in, then that resource is listed in the update right acquisition resource list corresponding to transaction 11. They are deleted from the storage section 61 and the update right transfer resource list storage section 91 (step AIG).
.

Next, the corresponding resource is deleted from the update right unacquired resource list storage section 7n corresponding to the transaction In, and the corresponding resource is added to the update right acquired resource list storage section 6n corresponding to the transaction 1n ( Step A 11).

The processing in steps 88 to All is executed in the same way for each transaction causing the deadlock, and when it is determined that the processing for all transactions has been completed (step A12), the second The process moves to steps AI3 to A20 in FIG.

When the processing of steps 8 to 8-All is completed for each transaction causing the deadlock, the second
As shown in Figure (C), first, one of the multiple transactions causing the deadlock is selected (step A13). Next, the update right request resource list storage section 5n and the update right acquisition resource list storage section 6n corresponding to the selected transaction, for example, transaction In, are referred to, and it is determined whether or not they match (step A14). ).

When the update right request resource list storage section 5n and the update right acquisition resource list storage section 6n match, an update request for the transaction ln is executed (step A15).

Next, the update right acquired resource list storage part an corresponding to the transaction in for which the update request process has been completed and the update right unacquired resource list storage part of other transactions are referenced, and the transaction in for which the update process has been completed acquires the update right. It is determined whether or not there are resources that have been requested to be updated by other transactions among the acquired resources (
Step A 1B).

If there is a resource that has been requested to be updated by another transaction among the resources for which the transaction ln that has completed processing has acquired the update right, that resource is deleted from the update right acquisition resource list storage unit 6n of the transaction In. (step 17), and thereafter, the corresponding resource is deleted from the update right unacquired resource list storage unit corresponding to any transaction requesting update of the resource, and
The corresponding resource is added to the update right acquisition resource list storage section (step A18).

The processing in steps A13 to A1g is executed in the same way for each transaction causing the deadlock, and when it is determined that the processing for all transactions has been completed (step A19),
In the next step A20, it is determined whether update requests for all transactions have been executed.

If the update requests for all transactions have been executed, the deadlock release process is completed. On the other hand, if there are transactions for which update requests have not been executed, step 88 in FIG. 2(B) is performed. The process from then on is executed again.

As described above, in this embodiment, a resource to be transferred is selected for each transaction, and among the resources to be transferred, the resource that is the target of a processing request and whose processing layer has not been acquired by another transaction is selected. transferred to that transaction. Therefore, even if a deadlock occurs, transactions will not have to wait forever for the processing layer to receive the resources they each need, and the deadlock can be efficiently released without sending an error back to the application program. I can do it.

In this case, acquired resources with a higher ranking than the lowest ranking of unacquired resources are selected as transfer candidate resources, but this is to improve the efficiency of selecting transfer candidate resources, and to avoid deadlock in this invention. The cancellation method is not limited to the selected method.

[Effects of the Invention] As described above, according to the present invention, update requests for each transaction can be executed sequentially, so that deadlocks can be efficiently released.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a system according to an embodiment of the present invention, and FIG. 2 is a flowchart illustrating the deadlock release operation of the system shown in FIG. 1. 10... Resource list management unit, 30... Database management unit, 51-5n... Update request resource list storage unit,
61-6n... Update right acquisition resource list storage unit, 71-
7n...Resource list storage unit for which update rights have not been acquired, 81...
Resource ranking list storage unit, 91 to 9n... Update right transfer resource list storage unit.

Claims (1)

[Claims] In a deadlock release method for a system that simultaneously accepts processing requests from a plurality of transactions for a database or file, the system comprises: a first storage means for storing ranking information pre-allocated to resources in the database or file; and each transaction. a second storage means for storing, for each transaction, resources for which processing rights have been acquired among the resources requested to be processed by the transaction, and resources for which processing rights have not been obtained among the resources requested to be processed by each transaction; With reference to the third storage means for storing resources for each transaction, and the first, second, and third storage means, a predetermined resource for which processing rights have not been acquired among the resources for which processing rights have been acquired is stored. Transfer candidate selection means for selecting a resource with a higher rank than a resource with a higher rank as a transfer target candidate resource for each transaction;
A fourth storage means stores the resources of the transfer target candidates selected by the transfer candidate selection means for each transaction, and a fourth storage means stores the resources of the transfer target candidates selected by the transfer candidate selection means, and refers to the third and fourth storage means, A dead transaction system comprising a transfer means for selecting a resource to be processed for which no other transaction has acquired processing rights among the resources, and transferring processing rights for the selected resource to a corresponding transaction. Unlock method.