KR20010055981A - Method for recovering main memory database system using stable memory - Google Patents

Abstract

PURPOSE: A method for recovering a main internal memory-resident type database using a secure storing device is provided to enhance a system performance by using a secure storing device for updating and backing-up data of a shadow page method, thereby not reflecting a log creation with respect to a change of a database and a log record. CONSTITUTION: After a system is re-booted, it is judged whether a transaction is started(802). If a transaction is not started, all pages of a backup database are loaded in a main internal memory-resident database(804). If a transaction is started, it is judged whether the corresponding page exists in useful page list(806). If the corresponding page does not exist in an available page list, it is judged whether the corresponding page exists in a backup page list(808). If the corresponding page does not exist in a backup page list, the corresponding page of the backup database is loaded in a shadow area of a secure storing device(810). In addition, the corresponding page is registered in the available page list(812). If the corresponding page exists in a backup page list, the corresponding page is registered in the available page list(812). In addition, the corresponding page is registered in the current page table(814). If the corresponding page exists in the available page list, the corresponding page is registered in the current page table. In addition, a working with respect to the current page is performed(816). The processes are repeated from the (806)stage.

Description

Recovery method of main memory resident database using safety memory device {METHOD FOR RECOVERING MAIN MEMORY DATABASE SYSTEM USING STABLE MEMORY}

The present invention relates to a method for recovering a main memory resident database, and more particularly, to use a safety memory device as a space for data update and backup of a shadow paging technique, and to generate and recover a log of a database change. The present invention relates to a main memory resident database recovery method capable of improving system performance by not reflecting log records, and a computer readable recording medium having recorded thereon a program for realizing the method.

In general, the database recovery technique is based on the log-based recovery technique and the shadow paging technique, and the existing main memory resident database system uses the log-based recovery technique or the log-based recovery technique and the shadow paging technique. .

1 is a block diagram of a conventional main memory resident database recovery system, and includes a main memory 10 including a main memory resident database 11 and a log buffer, and stores pages. And a log disk 30 for recording a log of the main memory resident database 11.

In the conventional main memory resident database recovery system having the above-described configuration, if the log-based recovery method is used, both the undo and redo operations are performed and the transaction is performed when the recovery process is performed. ) If you execute the undo operation when the revocation operation is performed, and the log and shadow paging based recovery method are used together, only the retry operation is performed when the transaction is canceled or restored.

In addition, the fuzzy checkpoint method for minimizing the impact of recovery processing on transactions requires twice the backup disk space to maintain database consistency, and the checkpoint is the most recent database content. Can be saved on the backup disk to shorten the log processing time during recovery.

However, the conventional main memory resident database recovery system as described above degrades the system performance because all processing for the database is recorded in the log, and since the generation, recording, and storage of the log is performed during the execution of the transaction, There is a problem of delaying execution time.

In addition, there is another problem of increasing system down time by delaying the processing of a new transaction by applying a log to recover a database before restarting the system in case of a system error.

In addition, the fuzzy checkpoint method has another problem in that an additional cost is required to double the space of the backup disk.

Therefore, the present invention devised to solve the above problems, by using the safe memory for the data update and backup of the shadow page technique by not reflecting the log record during the log generation and recovery operation for the database changes It is an object of the present invention to provide a method for recovering a main memory resident database using a safety memory device that can improve the performance of a system, and a computer-readable recording medium recording a program for realizing the method.

1 is a block diagram of an embodiment of a conventional main memory resident database recovery system.

Figure 2 is an embodiment configuration of a main memory resident database recovery system using a safety memory device to which the present invention is applied.

Figure 3 is a configuration diagram of one embodiment of a safety memory device according to the present invention.

4 is an explanatory diagram of a data structure of safety memory components according to the present invention;

Figure 5 is an embodiment processing flow diagram for a transaction processing method using a safety memory device according to the present invention.

Figure 6 is a flow chart of one embodiment of a transaction withdrawal processing method using a safety memory device according to the present invention.

7 is a flowchart illustrating a method for backing up a page using a safety memory device according to the present invention.

8 is a flow chart of an embodiment of a system recovery method using the safety memory device according to the present invention.

* Explanation of symbols for the main parts of the drawings

201: Main memory resident database 202: Safety memory

203: Backup Database 204: Transaction Manager

205: safety storage manager 206: backup manager

301: shadow area 302: backup area

303: Current page table 304: Available page list

305: backup page list 306: free page list

The method of the present invention for achieving the above object, in the main memory resident database recovery method applied to the main memory resident database recovery system using a safety memory device, the first step of processing a transaction using the safety memory device ; A second step of withdrawing a transaction using the safe storage device; A third step of backing up a page to a backup database using the safe storage device; And a fourth step of reloading the page used when a system error occurs using the safety memory device to the main memory resident database.

The present invention also provides a main memory resident database recovery system using a safety memory device having a microprocessor, comprising: a first function of processing a transaction using the safety memory device; A second function of withdrawing a transaction using said safe storage device; A third function of backing up a page to a backup database by using the safety memory device; And a computer-readable recording medium having recorded thereon a program for realizing a fourth function of reloading a page used at the time of a system error by using the safety memory device in a main memory resident database.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an embodiment of a main memory resident database recovery system using a safety memory device to which the present invention is applied.

As shown in the figure, the main memory resident database recovery apparatus using the safety memory device according to the present invention, the main memory resident database 201 and the correction of the pages of the main memory resident database 201 If required, a safety memory device 202 including a shadow area to which the page is copied, a backup database 203 for backing up pages and pages modified in the shadow area of the safety memory device 202, and the main memory resident A transaction manager 204 for processing general operations on pages recorded in the type database 201, a safety memory manager 205 for managing the safety memory device 202, and the safety memory device ( A backup manager 206 manages the backup operation and the recovery operation of the page through 202. Here, if a modification to a page of the main memory resident database 201 is requested, the page is copied after being copied to the shadow area of the safe memory 202, and updated after completion of the modification transaction. Reflected in the database 201. The modified page in the shadow area of the safety memory device 202 remains to perform a backup and is stored in the backup database 203 by the backup manager 206.

Now, the configuration of the safety memory device 202 will be described in detail with reference to FIG. 3.

3 is a configuration diagram of an embodiment of a safety memory device according to the present invention.

As shown in the drawing, the safety memory device according to the present invention includes a shadow area 301 for copying a page when a modification to a page of the main memory resident database 201 is requested, and the backup database. A backup area 302 shared with 203, a current page table (CPTable: CurrentPageTable) 303 that manages pages currently being used by a transaction, and a page that is currently being used or pages that have been backed up are available. UsableList 304, a backup page list 305 which the transaction manager has completed and which the backup manager 206 refers to to perform a backup of the page, and the backup area 302. It includes a free page list (FreeList) 306 for managing a blank page of the.

Here, the current transaction is in progress, that is, the list 303 of the current page table is added to the backup page list 305 at the completion of the transaction, and the transaction refers to the free page list 304 for page access, The list of backed up pages is registered in the free page list 304.

4 is a diagram illustrating a data structure of the safety memory device according to the present invention. The current page table 303, the usable page list 304, and the backup page list 305 described in FIG. The data structure 400 holds page information PID in the main memory resident database 201 and information S_Addr of the shadow area 301, and the free page list 306 is configured to display the shadow area ( 301 or a data structure 401 for holding information S_Addr of the backup area 302.

Next, a method of recovering a main memory resident database using the safety memory device according to the present invention will be described in detail with reference to FIGS. 5 to 8.

5 is a flowchart illustrating a transaction processing method using a safety memory device according to the present invention.

In general, since the main memory resident database 201 has no disk I / O, lock setting and information holding due to concurrent execution may reduce the overall system performance and execution time per transaction. To do it.

First, it is determined whether the page information is required when generating and completing a general transaction (500).

As a result of the determination 500, if there is a page information request, it is determined whether the corresponding page exists in the usable page list 304 (502).

In the determination result 502, if the page exists in the usable page list 304, the page is recorded in the current page table 303 (504), after processing the transaction (508), and step 500 is performed. Perform.

As a result of the determination 502, if the page does not exist in the usable page list 304, a new page is allocated from the free page list 306, and the page information is stored in the main memory resident database 201. After acquiring the page (506), the step 504 is performed.

If there is no page information request, the determination result 500 reflects the contents of the current page table 303 to the main memory resident database 201 (510), and the contents of the current page table 303. The backup page list 305 is registered (512).

6 is a flowchart illustrating a transaction withdrawal processing method using a safety memory device according to the present invention.

First, a transaction withdrawal request is received (600), all pages of the current page table 303 are deleted from the usable face list 304 (602), and a page for which transaction withdrawal is requested is added to the free page list ( After adding to 306 (604), the page is deleted from the current page list table 303 (606).

7 is a flowchart illustrating a method for backing up a page using a safety memory device according to the present invention.

First, it is determined whether the backup page list 305 is empty (700).

In response to the determination result 700, when the backup page list 305 is empty, the step 700 is performed again, and when the backup page list 305 is not empty, the pages of the backup page list 305 are stored in the safe state. It backs up to the shadow area 301 of the memory | storage device 202 (702).

Then, it is determined whether the backed up page exists in the usable page list 304 (704).

If the determined result 704 does not exist in the usable page list 304, the page is added to the usable page list 304 (706), and the backed up page is available. If present in the page list 304, the page is added to the free page list 306 (708).

8 is a flowchart illustrating a method for recovering a system using a safety memory device according to the present invention.

First, after restarting the system (800), it is determined whether the transaction has been started (802).

As a result of the determination 802, when the transaction has not started, all pages of the backup database 203 are loaded into the main memory resident database 201 (804), and when the transaction starts, the page is available. It is determined whether it exists in the list 304 (806).

As a result of the determination 806, if the page does not exist in the usable page list 304, it is determined whether the page exists in the backup page list 305 (808).

If the determined result 808 does not exist in the backup page list 305, the corresponding page of the backup database 203 is loaded in the shadow area 301 of the safety memory device 202 (810). In step 812, the page is registered in the usable page list 304.

In the determination result 808, if the page exists in the backup page list 305, the page is registered in the usable page list 304 (812), and the page is stored in the current page table 303. Register (814).

As a result of the determination 806, if the page exists in the usable page list 304, the page is registered in the current page table 303 (814), the operation on the page (816), The process is performed again from step 806.

In the system recovery method using the safety memory device according to the present invention as described above, backup is continuously performed asynchronously regardless of the recovery process, and if the contents of the backup database 203 are stored in the main memory resident database ( Even if a system error occurs in the process of loading in 201, the backup page list 305 is maintained in the safety memory device 202, thereby maintaining consistency.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited to the drawing.

As described above, the present invention uses a safety memory device as a space for data updating and backup of a paging technique, and a backup operation of a page is performed irrespective of a transaction operation, thereby burdening log processing when performing a transaction. By reducing the speed of transaction execution can be guaranteed, by using the shadow paging method, there is an effect that can significantly improve the speed of the transaction withdrawal or recovery.

Claims (8)

In the main memory resident database recovery method applied to the main memory resident database recovery system using a safety memory device, A first step of processing a transaction using a secure memory device; A second step of withdrawing a transaction using the safe storage device; A third step of backing up a page to a backup database using the safe storage device; And A fourth step of reloading the page used at the time of system error using the safety memory to the main memory resident database Main memory resident database recovery method using a safety memory including a. The method of claim 1, When the modification of the page of the main memory resident database is requested, the safety memory device manages a shadow area for copying the page, a backup area shared with the backup database, and pages currently being used by a transaction. A current page table, a usable page list for managing a page currently being used or a backup completed page, a backup page list for managing a transaction completed page, and a free page list for managing blank pages of the backup area. A main memory resident database recovery method using a safety memory device characterized in that the. The method of claim 2, The current page table, the usable page list and the backup page list each have a data structure for holding page information and information of the shadow area in the main memory resident database, wherein the free page list is the shadow area or the backup area. A main memory resident database recovery method using a safety memory device, characterized in that it has a data structure that maintains the information. The method according to any one of claims 1 to 3 The first step is, A fifth step of determining whether page information is required during the creation and completion of the transaction; A sixth step of determining whether a page exists in the usable page list if a page information request is found as a result of the fifth step; A seventh step of writing a corresponding page in the current page table and processing a transaction if the page exists in the usable page list as a result of the determination in the sixth step; An eighth step of obtaining a new page from the free page list and acquiring the corresponding page information page from the main memory resident database if the corresponding page does not exist in the usable page list as a result of the determination of the sixth step; And And a ninth step of reflecting the contents of the current page table in the main memory resident database and registering the contents of the current page table in the backup page list when there is no page information request. A method for recovering a main memory resident database using a secure memory device. The method of claim 4, wherein The second step, A tenth step of receiving a transaction withdrawal request and deleting all pages of the current page table from the available face list; An eleventh step of adding, to the free page list, the page requiring the transaction withdrawal; And And a twelfth step of deleting the page from the current page list table. The method according to any one of claims 1 to 3, The third step, A fifth step of checking information of the backup page list and backing up pages of the backup page list to a shadow area; A sixth step of determining whether the backed up page exists in the usable page list; A seventh step of adding the page to the usable page list if the backed up page does not exist in the usable page list as a result of the determination of the sixth step; And a eighth step of adding the corresponding page to the free page list when the backup page exists in the usable page list as a result of the determination in the sixth step. The method according to any one of claims 1 to 3, The fourth step, After restarting the system, determining whether a transaction has started; A sixth step of loading all pages of the backup database into the main memory resident database if the transaction is not started as a result of the determination in the fifth step; A seventh step of determining whether a corresponding page exists in the usable page list if a transaction is started as a result of the determination in the fifth step; An eighth step of determining whether the page exists in the backup page list if the page does not exist in the usable page list as a result of the determination of the seventh step; A ninth step of loading the page into the shadow area in the backup database and registering the page in the usable page list if the page does not exist in the backup page list as a result of the determination in the eighth step; A tenth step of registering the page in the usable page list and registering the page in the current page table if the page exists in the backup page list as a result of the determination in the eighth step; And As a result of the determination of the seventh step, if the page exists in the usable page list, after registering the page in the current page table, and using the safety memory device comprising the step of performing the operation for the page How to recover main memory resident database. In a main memory resident database recovery system using a safety memory device with a microprocessor, A first function of processing a transaction using a secure memory device; A second function of withdrawing a transaction using said safe storage device; A third function of backing up a page to a backup database by using the safety memory device; And A fourth function of reloading the page used at the time of system error by using the safety memory to the main memory resident database A computer-readable recording medium having recorded thereon a program for realizing this.