JPH02157943A - Data manipulation language instruction retesting system - Google Patents

Abstract

PURPOSE:To reduce a burden elating to error processing in a user program by removing the cause of an error in the execution processing part of a data manipulation language (DML) instruction and after that, re-executing the same DML instruction when any error is detected while the DML instruction to be described by the user program is executed and processed. CONSTITUTION:As a result to execute a DML instruction executing means 13, an error detecting means 14 decides whether the error is generated or not and an error recovering means 16 removes the generation cause of the error. After that, an entry load means 17 returns an entry point, which is formerly saved by an entry save mans 11, to an entry save area 41 which is secured in a main storing part 4. Simultaneously, a currency load means 18 returns currently information, which are formerly saved by a current save means 12, to currency save area 42 which is secured in the main storing part 4. Next, a re-executing means 19 delivers control to the entry save means 11. Thus, error processing is easily executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an instruction retry method when an error occurs when a database system using an electronic computer is accessed using data manipulation language instructions.

[Conventional technology]

Traditionally, data manipulation languages issued by user programs (Data Manipulation Language)
If an error is detected during processing of an instruction (hereinafter referred to as DML), the DML instruction is simply returned. Therefore, it is the responsibility of the user program to determine the error information and take appropriate processing.

[Problem to be solved by the invention]

In the above-described conventional processing upon detection of an error, it is necessary for the user program to determine the returned error information and perform corresponding processing based on the result. Therefore, it has the disadvantage of increasing the complexity and burden of processing the user program.

[Means to solve the problem]

The present invention provides a database system that accesses data records using DML instructions written in a user program, including an instruction execution unit that executes the DML instruction issued from the user program;
error detection means for detecting whether an error has occurred during execution of an instruction; and an error type for determining whether the error is recoverable or unrecoverable when the error detection means detects the occurrence of an error. a determining means, an error recovery means for removing the cause of the error that is recoverable, and a D that has caused the error in the instruction execution means after the cause of the error has been removed by the error recovery means;
and re-execution means for re-executing the ML instruction.

〔Example〕

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

Referring to FIG. 1, one embodiment of the present invention is composed of a DML processing section 1, a user program 2, a large capacity storage section 3, and a main storage section 4. , currency save means 12 , DML instruction execution means 13 , error detection means 14 , error type determination means 15 , error recovery means 16 , entry load means 17 , currency load means 18 , and re-execution means It consists of 19.

DML instruction 21 written inside the user program 2
At the time of execution, control is transferred to the DML processing unit (consisting of a program) 1 according to the type of DML instruction to be executed.

The entry save means 11 stores the address of the entrance of the DML processing section 10 to which control is transferred by the DML instruction 21 written in the user program 2, in the entry save area 41 secured within the main storage section 4. Next, the currency saving means 12 saves the currency information at the entrance of the DML processing section 1 (record key information necessary when executing the next DML command among the table information) into the main storage section 4. It is stored in the secured currency save area 42.

Thereafter, the DML instruction execution means 13 performs the search process requested by the DML instruction 21 written in the user program 2 by referring to the index area 31 in the database stored in the storage unit 3 and searching for the key value. By using a pointer, this is performed on the data area 32 where actual data is stored.

Next, the error detection means 14 detects the DML instruction execution means 13.
Determine whether an error has occurred as a result of executing.

If no error is detected, control returns to user program 2.

When an error is detected, the error type determining means 15 determines the type of the detected error, and as a result of the 0 determination that determines whether the error is recoverable, it is determined that the detected error is unrecoverable (for example, If the specified record does not exist or the request is to write a record with attributes different from the table definition), error information regarding this error is returned to the user program 2 and control is returned. On the other hand, if it is determined that the error is a recoverable error such as deadlock, the error recovery means 16 eliminates the cause of the error.

After removing the cause of the error, the entry loading means 17 saves the entry into the entry save area 41 secured within the main storage unit 4.
In addition to restoring the entry point previously saved by the entry saving means 11, the currency loading means 1
8 restores the currency information previously saved by the currency save means 12 to the currency save area 42 secured within the main storage section 4.

After this, the re-execution means 19 executes the entry loading means 17.
Based on the entry point restored by , control is passed to the entry save means 11 in the same way as when control was passed from the DML instruction 21 of the user program 2 .

As a result of the execution by the DML instruction execution means 13 again, if the error detection means 14 detects the error again and the error type determination means 15 determines that the error is recoverable, the error recovery means 16 Entry loading means 17
and the re-execution means 19 via the currency loading means 18.
may be carried out, and the series of measures may be repeated.

〔Effect of the invention〕

As explained above, in the present invention, when an error is detected during the execution processing of a DML instruction written in a user program RAM, the cause of the error is removed in the DML instruction execution processing section, and then the same DML instruction is executed. By re-executing the instructions, the burden associated with error handling in the user program can be greatly reduced.

The effect of the present invention can be most expected in processing when a deadlock occurs. Conventionally, when a deadlock occurs, error information is simply returned to the user program, which requires the user program to take the trouble to write the process to be performed when a deadlock occurs. According to the present invention, all processing when deadlock occurs is resolved by the DML instruction execution processing unit, so error information regarding deadlock is not returned to the user program. Therefore, there is no need to describe deadlock processing in the user program, and the burden on creating the user program is greatly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention. l...DML processing unit, 2...user program, 3...mass storage unit, 4...
・Main memory section, 11...Entry saving means, 1
2... Currency save means, 13...
DML instruction execution means, 14...Error detection means, 15...Error type determination means, 16...
...Error recovery means, 17... Entry loading means, 18... Currency loading means, 19...
. . . Re-execution means, 21 . . . DML instruction, 3
1... Index area, 32...
Data area, 41...Group/Entry save area, 4
2. Dan/currency save area. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Scope of Claim] A database system that accesses data records using data manipulation language instructions written in a user program, comprising: instruction execution means for executing the data manipulation language instructions issued from the user program; Error detection means for detecting whether an error has occurred during execution of a data manipulation language instruction; and when the error detection means detects the occurrence of an error, it determines whether the error is recoverable or unrecoverable. error type determining means for determining the error type; error recovery means for removing the cause of the recoverable error; and after the error recovery means removes the cause of the error, the instruction execution means re-executes the data manipulation language instruction that caused the error. A data manipulation language command retry method characterized by comprising: re-execution means for causing