JPH04111026A - Write system for updating history information to data base - Google Patents

Abstract

PURPOSE:To curtail the output waiting time of updating history information, and to improve the processing capacity by issuing a write request to an external storage device of updating history information, and thereafter, continuing a transaction processing without waiting for the end of write, and taking confirmation of write before the transaction processing is finished at the latest. CONSTITUTION:After issuing a write request to an external storage device 7 of updating history information 11, a transaction processing is continued without waiting for the end of write, and confirmation of write is executed before the transaction processing is finished at the latest. That is, at the time of outputting the updating history information 11 to the external storage device 7, it is executed by dividing it into an output request and an output confirmation. In such a way, the output waiting time of the updating history information 11 is curtailed, and the processing capacity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to transaction processing, and more particularly to a method for writing update history information to an external storage device accompanying database updates that occur during transaction processing.

[Prior Art] The most important point in failure recovery is to guarantee user business transactions. Here, a transaction is a collection of logical processes of user business. Update history information is necessary for database failure recovery. The update history information needs to be stored on an external storage device in order to cope with power-off of the processing device. Furthermore, in the relationship between the update history information and the user record to be updated, the update history information must be output to the external storage device before the user record. this is,
If the user record is output first, if a failure such as a power outage occurs after the user record is output but before the update history information is output, the database recovery process will not be possible because there is no update history information. .

In addition, regarding disaster recovery, for example, Japanese Patent Laid-Open No. 61-1
51754, JP-A-2-87242, and the like.

[Problems to be Solved by the Invention] Conventionally, user records output to an external storage device have been buffered on main memory. The unit of this buffering is generally a physical data area unit (page). In a general database that performs exclusive control on a record-by-record basis, there are multiple records in one page, so different records in the same page may be accessed by different tasks. To accommodate this, buffers are managed in a system common area. This means that when a transaction ends in a certain task and a user record is output to an external storage device, user records of other tasks within the same page will also be output. That is, since it is not known when the user record will be output to the external storage device due to the movement of other tasks, the update history information must always be output immediately due to the relationship between the update history information and the output order of the user records. The biggest problem with this conventional method is that it takes time to output the update history information. User records can be buffered, but since the update history information is output immediately, the next process related to the same transaction must wait until the output to the external storage device is completed, and each time the user record is updated There was always one external storage device output wait.

An object of the present invention is to reduce the output waiting time of update history information and improve processing capacity.

[Means for solving the problem] The above purpose is to continue transaction processing without waiting for the end of writing after issuing a write request for update history information to an external storage device, and to continue transaction processing until the end of transaction processing at the latest. This is achieved by confirming the writing.

[Effect] By using a task-specific local buffer that is not affected by other tasks as a buffer for outputting update history information, and when the task needs to output a page containing user records. , refer to the update history information of other tasks, and check the output completion for those for which an output request has already been issued, and perform both the output request and the output completion confirmation for those for which no output request has been issued. After that, by outputting the page where the user record is stored, it is possible to guarantee the output order of the user records of other tasks and the update history information.

[Example code] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

Figure 1 is for explaining the update history output management method in relation to each process. 1 is the user's business program, 2 is the operating system entrusted with data processing from the business program 1, and 3 is the system for the database. 4 is a data area on the main memory where record groups and update history information for processing data from user programs are stored; 5 is a page buffer that stores user records; 6 is a database access control unit that is in charge of processing; an update history information buffer that stores update history information;
7 is an external storage device such as a magnetic disk in which a database and update history information are stored; 8 is a database in which user records are stored; 9 is a user record; 10 is a data area 4 and a user record 9 on the main storage device. 11 is update history information that stores the update history of user records; 12 is an update history information area that manages and stores update history information; 13 is an external storage device 7 for storing the contents of the database and update history information; A channel device 14 is used for inputting and outputting data to and from the external storage device 7, and is an input/output control unit that controls inputting and outputting data to and from the external storage device 7.

Figure 2 shows the relationship between the update history information buffer corresponding to a task and the update history information area on the external storage device.
5 is the first task, 1-a is a business program running in task 15, 6-a is update history information of the process executed by the program and a buffer for storing it, 16 is the second task, 1-b is the business program running in task 16, 6- is the update history information of the process executed by the business program 1-b and a buffer that stores it, and 7 is external storage such as a magnetic disk in which updated track information is stored. device, 12
is an update history information area for managing and storing update history information, 1
7 is an update history information area allocated for task 15, 11
-a is the update history information of task 15, 18 is the update history information area allocated for task 16, and 11-b is task 16
This is update history information.

When a user record is updated (including addition and deletion) in the business program 1-a of task 15, the update history is stored in the update history buffer 6-a. Similarly, task 1
When a user record is updated by the business program 1-b of No. 6, the update history is stored in the update history buffer 6-b. Since these two buffers are secured in local areas specific to each task, serial control is not necessary and parallel processing is possible. Also, when the task in question ends and the update history information is no longer needed, the update history information up to that point will be deleted, but since it is in a separate area on the external storage device, it will affect the update history information of other tasks. Processing can be performed without giving up space, and no wasted space is created.

FIG. 3 shows a management method for pages that store user records, with reference numeral 19 a table for managing page reference/update states and buffer addresses, 5 a page buffer for storing user records, 15, 16 . n is a task that executes a business program.

The page management table 19 manages the state of pages. By referring to this table, the usage status of the page becomes clear, and it can be determined whether there is a task other than the own task that is updating the page. When it is necessary to output user records to an external storage device in a certain task, check this table and, if the same page is being updated in another task, change the output order of user records and update history information of other tasks. To protect this, update history information of other tasks is output to an external storage device.

Figure 4 shows the relationship between task management information, and shows 20
is the only database management information in the system, 1
5,16. n is a task, 21 is task management information for managing the task, and 6 is an update history management information buffer corresponding to the task.

By referring to the page management table mentioned above, when it becomes necessary to output update history information of other tasks, this task management information 21 is searched to determine the task that needs to be output to the external storage device 7. Finds the update history information buffer address of the task determined in , and outputs the contents of the buffer to an external storage device.

Figure 5 shows the flow of the business program 1 and the order of record transfer to the buffer and output to the external storage device. 22 is the flow of the business program from the start to the end of the transaction, and 23 to 32 are database access control. This is buffer transfer and external storage device output processing performed by unit 3.

When a record update request (update of record A) comes from the business program 1, the user record is first transferred to the page buffer 5 (23), and then a request to output update history information for the current update request (24) and the update history are sent. The information output is confirmed (25). At this point, control is returned to the business program 1, and the business program 1 continues the transaction processing. Next, when a record update request (update of record B) comes, the user record is similarly transferred to the page buffer (26). Here, a request is made to the external storage device 7 to output the contents of the page buffer 5 in which the previous record A is stored (27). Next, an output request (28) for the update history information for the current update request is made, and at this point, control is returned to the business program 1 without immediately confirming the output, and the business program 1 continues the transaction processing. By returning control to the business program without checking the output in this way, the response of the business program is improved.

At the end of transaction processing performed by a business program, all information must be output to the external storage device, so the user record output confirmation (29, 31, 32) and update history information output confirmation (30) are performed together. By dividing the output to the external storage device into an output request and an output confirmation, as in the case of 0 or more, it is effective to improve performance.

Please note that the update history information output request for record A update (
24) and confirmation of output of update history information (25) are the first record updates, so they are output immediately. If there is another record C update following the update of record B, the output of the update history information of record B can be confirmed at this point.

[Effects of the Invention] As is clear from the above description, when outputting update history information to an external storage device, performing the output request and output confirmation separately is effective in improving performance.

In addition, by buffering the update history information and managing it in a local buffer, serial control is not required, the number of outputs to the external storage device can be reduced, and the area management on the external storage device is effective. .

In addition, it has task management information and page management information, and by managing the external storage output status of not only the relevant task but also the back task, guarantees the number of times the user records and update history information required for failure recovery are output to the external storage device. This is effective in improving reliability.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram for realizing the present invention, Figure 2 is a system configuration diagram for realizing the present invention.
The figure is a diagram to explain the relationship between the update history information buffer and the external storage device, Figure 3 is a diagram showing management information for page management, and Figure 4 is a diagram showing management information for task management. FIG. 5 is a diagram for explaining the order in which user records and update history information are output to an external storage device. DESCRIPTION OF SYMBOLS 1... Business program, 3... Database access control unit, 5... Page buffer, 6... Update history information buffer, 7... External storage device, 9... User record. 10...page. 11...Update history information.

Claims (1)

[Claims] 1. In a method of writing update history information to an external storage device due to a database update that occurs during transaction processing, after issuing a write request for the update history information to the external storage device, without waiting for the end of the writing. A method for writing update history information to a database, characterized in that the transaction processing is continued and the writing is confirmed at the latest until the end of the transaction processing.