JPS6354638A - Deadlock releasing system - Google Patents

Abstract

PURPOSE:To improve the productivity of a program by detecting a reference system program when a deadlock has been generated, executing automatically a rollback processing of this reference system program and a re-execution processing of a data base operating instruction by a data base managing system and releasing the deadlock. CONSTITUTION:A data base operating instruction storage means 3 stores an issuing state of a data base operating instruction at every process, a cancel process detecting means 5 detects a process which is executing only an input to a data base from in process group related to a deadlock based on storage information stored in the data base operating instruction storage means 3, when the deadlock has been generated, and a canceling/re-executing means cancels and re-executes the data base operating instruction which is being executed of the process which has been detected by a cancel process detecting means 6. Accordingly, when the deadlock is generated, the reference system program is detected and a rollback processing of this reference system program and a re-execution processing of the data base operating instruction can be executed automatically by a data base managing system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a deadlock release method, and more particularly to a deadlock release method when a deadlock occurs in a database management system that performs commitment control.

(Prior Art) Conventionally, in this type of deadlock release method, when a deadlock occurs, a database management system unilaterally returns the deadlock status to the process that detected the deadlock, and the process to which the deadlock status was returned is The deadlock was released by performing rollback processing.

[Problem that the invention seeks to solve]

The conventional def lock release method described above has the following drawbacks.

(1) A program that only performs input because it unilaterally notified the deadlock status to the process that caused the first deadlock (hereinafter referred to as a reference program)
It is necessary to incorporate processing for deadlock into all programs, including programs.

(2) If a deadlock occurs between a reference program and an update program other than the reference program, the reference program is notified of the deadlock status and has the reference program perform rollback processing. However, depending on the timing, it is uncertain which party will be notified.

In view of the above-mentioned points, an object of the present invention is to detect a reference program when a deadlock occurs, and to automatically perform roll bank processing and re-execution processing of database operation instructions for this reference program in a database management system. The purpose of this invention is to provide a deadlock release method based on the following methods.

[Means for solving problems]

The deadlock release method of the present invention, in a database management system performing commitment control, includes a database operation instruction storage means that stores the issuing status of database operation instructions for each process, and a database operation instruction storage means that stores the database operation instruction issuance status for each process when a deadlock occurs. A canceling process detecting means detects a process that performs only manual operation on the database from among the processes related to this deadlock based on the recorded memory information, and a process detecting process detected by the canceling process detecting means It has cancel/re-execute means for canceling and re-executing the execution of the database operation command being executed.

[Effect]

In the deadlock release method of the present invention, the database operation command storage means stores the issuing status of the database manipulation command for each process, and the canceling process detection means stores the storage state stored in the database manipulation command storage means when the deadlock occurs. A process that is only inputting information to the database is detected from among the processes related to the deadlock, and the cancel/re-execution means cancels the database operation during execution of the process detected by the process detection means. Cancels the execution of the command and re-executes it.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

Referring to FIG. 1, one embodiment of the present invention includes a user process 1, a database operation command analysis means 2, a database operation command storage means 3, and a deadlock detection means 4.
, a cancellation process detection means 5, and a cancellation/re-execution means 6.

Referring to FIG. 2, the processing in the database operation instruction/tα means 3 includes a database update command determination step 21 and a database update flag on setting step 2.
It consists of 2.

Referring to FIG. 3, the processes in the cancel process detection means 5 include a process number setting step 31, a database update flag on judgment step 32, an H & process judgment step 33, a next process number setting step 34, and a reference process number setting step 34. It consists of a none setting step 35 and a cancel process setting step 36.

Referring to FIG. 4, the processing in the cancel/re-execution means 6 consists of a currency information saving step 41, a rollback processing execution step 42, a currency information restoration step 43, and a database operation command re-execution step 44.

Next, the operation of the deadlock release method of this embodiment configured as described above will be explained.

When the user process 1 issues a database manipulation command, control is transferred to the database manipulation command analysis means 2.

The database operation instruction analysis means 2 first calls the database operation instruction writing 19 means 3. The database operation instruction storage means 3 determines whether the database operation instruction is a database update instruction (step 21). If the database operation command is a database update command, the database update command flag (hereinafter referred to as update flag)
is set to on (step 22). Note that the update flag is initialized to off at the start of the process.

Next, the database operation command analysis means 2 calls the deadlock detection means 4. The deflock detection means 4 determines whether an access request to the database based on a database operation command causes a deadlock. If a deflock is not caused, control is returned to the database operation instruction analysis means 2. If a deflock occurs, the cancel process detection means 5 is called.

The canceled process detection means 5 detects whether a reference program exists in the process group that caused the deadlock. Specifically, the canceled process detection means 5 searches for the first process from the queue that manages the process group that caused the deadlock, and sets its process number in the work area P (step 31).
. Next, it is checked whether the update flag of the process indicated by the process number set in the work area P1 is on (step 32). If the update flag is on, the process that caused the default lock can be run eight times (step 33). If it is not the last process, the process number of the next process in the queue of processes that caused the deadlock is set to P, step 34), and the process returns to step 32. If it is the last process as determined in step 33, it means that there is no reference system program in the process group that caused the deadlock, and the deadlock detection means 4 and database operation instruction analysis means 2 and notifies user process 1 of the deadlock status (step 35). Therefore, when a deadlock occurs between update programs, the roll bank process is performed by the user process 1 as before. If the update flag is not on in the determination in step 32, the process set in the work area P+ is a reference program, so the deflock detection means 4 considers this process to be a canceled process.
(Step 36).

The deadlock detection means 4 notifies the cancellation/re-execution means 6 of the process notified from the canceled process detection means 5. The cancel/re-execute means 6 cancels and re-executes the execution of a database operation command that is currently being executed. Specifically, the cancel/re-execute means 6 first saves the force range information of the process to be canceled into the work area S (step 41). This is because the force range information becomes unstable in the rollback process, so the force range information is restored after the rollback process. next,
Cancels the execution of a database operation instruction that is currently being executed,
Rollback processing is performed on the cancel process to release the deadlock (step 42). Subsequently, the force range information that has become unstable due to the roll bank processing is restored with the contents of the work area S1 (step 43).

Thereafter, the canceled database operation command is re-executed (step 44).

If deadlock occurs again, deadlock detection means 4. The processes of the cancellation process detection means 5 and the cancellation/re-execution means 6 are repeatedly executed.

Note that in the above embodiment, the update flag to determine whether it is a reference program is initialized at the start of the program, but if this is done at the time of commit processing and roll bank processing, it will be more precise. Fine control becomes possible.

〔Effect of the invention〕

As explained above, the present invention does not unilaterally notify the deadlock status to the process that caused the deadlock when a deflock occurs, but detects a reference program and executes rollback processing and database operation instructions for the reference program. The database management system automatically performs the re-execution process to release deadlocks, resulting in the following effects:

fi+ Since the reference system program is not notified of the defrofter status, the reference system program does not need to incorporate processing for deadlock.

Thereby, the productivity of the program can be improved.

(2) When a deadlock occurs between a reference program and an update program, the deadlock is released by performing roll bank processing for the reference program, so the overhead at the time of deadlock release is reduced. I can do it.

(3) By limiting the number of update programs to be executed simultaneously to one zero in the database management system, it becomes possible to eliminate the need for deadlock processing in all programs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a flowchart showing the processing in the database operation command storage means in the figure; FIG. 3 is a flowchart showing the processing in the cancel process detection means during the first round; FIG. FIG. In the figure, l...User process, 2...Database operation instruction analysis means, 3...Database operation instruction storage means, 4...Deadlock detection means, 5.Cancellation process detection means, 6. ...It is a means of canceling and re-executing.

Claims (1)

[Scope of Claim] A database management system that performs commitment control includes: database operation instruction storage means for storing the issuing status of database operation instructions for each process; Cancellation process detection means for detecting a process that is only making input to a database from among the processes related to this deadlock based on stored information, and a database of running processes detected by this cancellation process detection means. A deadlock release method comprising: cancel/re-execute means for canceling and re-executing execution of an operation command.