JPH0256037A - Detecting system for page breakdown of data base - Google Patents

Abstract

PURPOSE:To constitute the title system so that a page breakdown of a data base can be detected when a central processor, etc., are stopped by adding '1' to an updating counter of the head of a data base page and setting its contents in advance to an updating counter of the end. CONSTITUTION:In order to update a data base page 1, the page 1 is inputted to a page input/output buffer 3 from an external storage device 2. Subsequently, the page 1 is updated, and thereafter, at the time of outputting the page 1 to the external storage device 2, '1' is added to a value (a) of an updating counter 4, the contents of the counter 4 are set to an updating counter 5 and an output processing is executed. In this case, when three physical blocks 7, 8 and 9 are outputted normally and the page 1 is not broken down, the counter 4 and 5 coincide with each other, therefore, it can be confirmed that the page 1 is not broken down. On the other hand, when a central processor, etc. are abnormal, the counter 4 and 5 do not coincide with each other, therefore, the page breakdown can be detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a database system, and in particular, when inputting/outputting a database page consisting of one or more physical blocks,
The present invention relates to a database page destruction detection method suitable for cases where a database page is destroyed due to physical block removal or physical block destruction.

[Conventional technology]

In the conventional method, control information that does not become zero in terms of software is placed at the end of a database page, and when the central processing unit, etc. stops due to a power failure during the process of outputting the database page to an external storage device, the zero data is transferred to the external storage device. Database page corruption was detected using the fact that the control information of the database page becomes zero as it is transferred to the device. However, in the method using control information, if a database page is composed of one or more physical blocks, and the central processing unit, etc. stops due to a power failure while outputting the first or intermediate physical block, In this case, only the first block is transferred with zero digits and the subsequent physical blocks are not transferred, and if an intermediate block is being output, normal data is transferred from the first block to the physical block before the relevant block. Zero data was transferred to the block and no transfer processing was performed after that block, and the physical block in which the control information was placed was not destroyed, so database page corruption could not be detected.

Incidentally, an example of a document relating to this type of data destruction detection is JP-A-56-74756.

[Problem to be solved by the invention]

The conventional method described above does not take into consideration cases where a database page is composed of one or more physical blocks, and the central processing unit may stop due to a power failure while outputting the beginning or middle block of a database page. There is a problem in that when a database page is destroyed, the destruction cannot be detected.

An object of the present invention is to enable database page corruption to be detected, even if a database page consisting of one or more physical blocks is corrupted in any physical block, thereby improving the reliability of a database system. The purpose of this invention is to provide a page destruction detection method.

[Means to solve the problem]

The above purpose is to provide an update counter area that stores a value of 1 or more at the beginning and end of a database page, and when outputting a database page to an external storage device, add 1 to the update counter at the beginning and update it at the end. Set the contents of the first update counter to the counter and output it.
This is achieved by checking whether the first update counter and the last update counter match when inputting a database page from an external storage device, and if they do not match, it is detected that the database page has been destroyed.

[For production]

The process of outputting a database page to an external storage device operates by adding 1 to the update counter at the beginning of the database page, setting the content in the update counter at the end, and outputting the result. As a result, the start and end update counters will not match when a database page is output, when the page is destroyed, such as when the central processing unit is stopped due to a power failure and the last physical block cannot be output.

It is now possible to detect database page corruption and prevent malfunctions.

〔Example〕

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

FIG. 1 is an explanatory diagram of the update counter when the database page output operation is normal.

In Figure 1, database page 1 consisting of three physical blocks 7.8°9 is input to external storage device 2.
, output P will be explained.

External storage device l to update database page 1
! 2, database page 1 is input to the database page input/output buffer 3. After updating database page 1, database page 1 is transferred to external storage device i.
When outputting P to 2, add 1 to the value a of update counter 4 (
Step 81), set the contents of the update counter 4 in the update counter 5 (Step 82), and output P processing (Step 8
Do 3). At this time, three physical blocks 7.8.9
is output normally and database page 1 is not destroyed, when database page 1 is re-inputted (step 91), update counter 4 and update counter 5 are
Since they match, it can be recognized that database page 1 has not been destroyed (step 94).

Next, output database page 1 to external storage device 2 P
When inputting database page 1 again after the central processing unit, etc. has stopped due to a power failure and database page 1 is in a corrupted state without being output properly, the following is a method for detecting page corruption in the database when inputting database page 1 again. Examples of three cases will be explained.

(1) In Figure 2, if the central processing unit, etc. stops due to a power failure during the output P of the first physical block 7, zero data is transferred to the physical block 7, and the data and base page 1 become destroyed. ing. Therefore, when database page 1 is inputted again as shown in Fig. 3, update counter 4 becomes zero and becomes 9, which matches update counter 5 (step 93). Destruction of a page in a state of destruction to which zero data has been transferred can be detected (step 95).

(2) In FIG. 4, if the central processing unit etc. stops due to a power failure during the output of the intermediate physical block 8, the database page 1 of the external storage device 2 will be in an updated state because the physical block 7 has been output normally. , physical block 8 is in a state where zero data has been transferred.

The physical block 9 is in a destroyed state in which no output processing has been performed and it has not been updated.

Therefore, when database page 1 is manually updated again as shown in FIG. 5, update counter 4 and update counter
Since there is a difference between them and they do not match (step 95), it is possible to detect page corruption in a database in which zero data is transferred to an intermediate block of the database, and the blocks from the block to which the zero data was transferred to the final block are not updated.

(3) In FIG. 6, if the central processing unit, etc. stops due to a power failure during the output of the final physical block 9, the database page l of the external storage device 2 will be transferred to the physical block 7.8.
is in a state where it has been normally output and updated, and physical block 9 is in a state where zero data has been transferred and is in a destroyed state. Therefore, as shown in FIG. 7, when the database page 1 is inputted again, the update counter 5 becomes zero and does not match the update counter 4 (step 95).

It is possible to detect page corruption in a corrupted database where zero data is transferred to the last block of the database.

As described above, according to this embodiment, page destruction of a database can be detected no matter which physical block of the database page is destroyed.

〔Effect of the invention〕

According to the present invention, if the central processing unit, etc. is stopped due to a power failure during output processing of a database page composed of one or more physical blocks, and the database page is destroyed, which physical block is destroyed? This has the effect of improving the reliability of the database system, since page corruption in the database can be detected even if the database is corrupted.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an update counter when the database page output operation is normal according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram when an abnormality occurs while outputting the first block of the database page. Figure 3 is an explanatory diagram when inputting a database page in which the first block of the database page is in a destroyed state, and Figure 4 is an illustration when the middle block of the database page is being output.
An explanatory diagram when an abnormality occurs. Figure 5 is an explanatory diagram when inputting a database page whose intermediate block is in a destroyed state, and Figure 6 is an illustration when the final block of the database page is being output.
An explanatory diagram when an abnormality occurs. FIG. 7 is an explanatory diagram when inputting a database page in which the last block of the database page is in a destroyed state, FIG. 8 is a flowchart of the database page output process according to the embodiment of the present invention, and FIG. 9 is a diagram of the database page input process. It is a flowchart. 1... Database page, 2... External storage device,
3...Database page input/output buffer, 4,5...
...Update counter, 6...Control information, 7,8.9...
・Physical block, P...output, G...input, a...
- Update counter value. A prisoner? mouthful η

Claims (1)

[Claims] 1. In a database system that stores a database in one or more database pages consisting of one or more physical blocks on an external storage device, an update counter area is provided at the beginning and end of each database page, and the database When outputting a page to an external storage device, update the relevant counter, then output it, and when inputting a database page from the external storage device, check whether the update counters of the first part and the last part match. A database page corruption detection method characterized by detecting the presence or absence of database page corruption.