KR20040050958A - Memory database back-up apparatus by duplicating management and method thereof - Google Patents

Abstract

PURPOSE: A backup device for a memory database through dual management and a method thereof are provided to minimize a data processing response time of a database while efficiently performing the backup of a main memory database. CONSTITUTION: A memory DBMS(DataBase Management System)(30) processes a data process request of a user or an application program(35) by loading the database stored in a sub memory to an original memory database area of a main memory, and stores the processed data processing request to a log area in an original memory database area. A duplicator(38) stores/duplicates the database stored in the original memory database area to a copy memory database area of the main memory, and reflects the data processing request to the database stored in the copy memory database area. A log controller(37) withdraws/transfers the data processing request stored in the log area to the duplicator according to the log data request of the duplicator. An OS(Operating System) is equipped with a system call reflecting a changed page to the database stored in the sub memory by monitoring the changed particulars in the copy memory database(36).

Description

Memory database back-up apparatus by dual management and method thereof {Memory database back-up apparatus by duplicating management and method

The present invention relates to a memory database backup device and a method thereof, and more particularly, to a memory database backup device and a method for dually managing a memory database in order to efficiently write changed pages on a disk in a database loaded and operated on the main memory. It is about.

Existing commercial database management system (hereinafter referred to as DBMS) has implemented a database on disk. Such a conventional DBMS is excellent in terms of stability, but has a limitation in performance due to an input / output operation that accesses a disk in a field requiring real-time data processing.

However, in recent years, the price of main memory is decreasing and the degree of integration is increasing. Therefore, a computer system equipped with a large main memory at a relatively low price is widely used. As a result, a main memory database capable of operating in real time by residing a database stored in an existing disk in main memory has become possible.

However, unlike the disk, the main memory has characteristics such as volatility and vulnerability, so that the contents stored in the main memory may be lost or changed due to the power of the system or the influence of other programs. . In preparation for such a database corruption, the memory DBMS periodically performs a backup operation of writing changed pages in main memory to disk.

In the case of a memory DBMS installed on a UNIX system, mmap, a system call that maps files on disk to the memory address space, is used for such backup operations. At this point, the operating system monitors the changes in the mapped main memory space and automatically reflects the changes in the files on disk.

As shown in FIG. 1, in the memory database backup method according to the related art, the DB core engine 21 of the memory DBMS 20 may use a database on the main memory according to an application 25 or a user's data change request. At 22, the corresponding data is changed, and mmap 24, which is part of the operating system, performs a task of backing up the changed pages in the same main memory database 22 to the disk 23. However, according to such a backup method, the database 22 change operation on the main memory and the backup operation of the changed page collide, and the response sent to the application 25 or the user is changed after the backup operation of the changed page. Can be slowed down. In most operating systems, the processing time for disk I / O related system calls is not slow enough to interfere with the behavior of real-time applications, but for fault tolerant systems, disk I / O related system calls are handled. If the time is considerably slow and the conventional memory database backup method is adopted, the operation of the real-time application may be hindered.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a memory database backup device and method thereof capable of minimizing data processing response time of a database while efficiently performing a main memory database backup. It is for the second purpose.

1 is a functional configuration diagram of a memory database backup device according to the prior art.

2 is a configuration diagram of a computer system in which a memory database backup apparatus according to the present invention is implemented.

3 is a functional configuration diagram of a memory database backup apparatus according to the present invention.

4 is a general flowchart of a memory database backup method according to the present invention.

5 is a flow chart for explaining the operation of the replication unit and the log control unit of the present invention.

In order to achieve the above first object, the memory database backup apparatus according to the present invention includes a CPU; Auxiliary memory for storing a database; A main memory for storing a program executed by the CPU and data to be processed; A memory DBMS that loads a database stored in auxiliary memory into an original memory database area of main memory to process a data processing request of a user or an application, and stores the processed data processing request in a log area within the original memory database area; A copy unit for copying a database stored in the original memory database area and storing the copy stored in the copy memory database area of the main memory, and reflecting the data processing request provided by the generation of the log data request to the database stored in the copy memory database area; A log control unit for retrieving a data processing request stored in a log area according to the log data request of the replication unit and transferring the data processing request to the replication unit; And an operating system having a system call that monitors changes in the copy memory database area and reflects the changed pages to the database stored in the auxiliary memory.

In order to achieve the above second object, the memory database backup method according to the present invention comprises the steps of: (a) loading the database stored in the auxiliary memory to the original memory database area of the main memory; (b) copying the database stored in the original memory database area and storing the copy in the copy memory database area of the main memory; (c) the memory DBMS processing a data processing request of a user or an application for a database stored in an original memory database area, and delivering the processing result to the user or application in response; (d) storing, by the memory DBMS, the processed data processing request in a log area in the original memory database area; (e) retrieving the data processing request stored in the log area and forwarding the data processing request stored in the log area according to the log data request of the copying unit; (f) reflecting the transferred data processing request to the database stored in the copy memory database area; And (g) the system call monitoring changes in the copy memory database area and reflecting the changed pages to the database stored in the auxiliary memory.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1, a computer system 1 in which a preferred embodiment of a memory database backup device according to the present invention is implemented is a computer having at least one central processing unit (CPU) 6 and a memory device 3 ( 2) and an input device 10 and an output device 11. The components of computer system 1 are interconnected by at least one bus structure 12.

The illustrated central processing unit 6 is an arithmetic / logical arithmetic unit (ALU) 7 for performing arithmetic and logical operations, a register set 8 for temporarily storing data and instructions, and the operation of the computer system 1. And a control device 9 for controlling the control. Since the central processing unit 6 used in the present invention is not limited to a specific structure manufactured by a specific manufacturer, any type of processor having a basic configuration as described above is possible.

The memory device 3 has a high speed main memory 4 and an auxiliary memory 5 used for long term storage of data. The main memory 4 is composed of RAM (Random Access Memory) and ROM (Read Only Memory) semiconductor chips, and the auxiliary memory 5 is a floppy disk, a hard disk, a CD-ROM, a flash memory, and an electric, magnetic, optical Or an apparatus for storing data using another recording medium. In addition, the main memory 4 may include a video display memory for displaying an image through a display device. Those skilled in the art will understand that the memory device 3 may include various replaceable components having various storage capacities.

The input device 10 may include a keyboard, a mouse, a physical transducer (eg, a microphone), and the like, and the output device 11 may include a display, a printer, a physical transducer (eg, a speaker), and the like. Also, devices such as network interfaces or modems can be used as input / output devices.

The computer system 1 is equipped with an operating system, a memory DBMS and at least one application program. The operating system is a set of software that controls the operation of the computer system 1 and the allocation of resources. The operating system includes a variety of system calls available to the application, which are requested by the user using the computer resources available through the operating system. Is a set of software that performs a task. All of these are stored in the memory device 3 shown. As a result, the memory database backup apparatus according to the present invention is implemented as a combination of the computer system 1 and the software installed and operated in the computer system 1.

2 and 3, a preferred embodiment of the memory database backup apparatus according to the present invention is a CPU 6, an auxiliary memory 5, a main memory 4, a memory DBMS 30, a replicator (38), a log controller (37), and an operating system (34).

The auxiliary memory 5 stores a database 33, and the main memory 4 includes a memory DBMS 30, a replication unit 38, a log control unit 37, and an operating system 34 by the CPU 6. The program to be executed and the area where the original memory database and the copy memory database will be loaded are reserved.

The memory DBMS 30 loads the database 33 stored in the auxiliary memory 5 into the original memory database area of the main memory 4. Accordingly, the DB core engine 31 of the memory DBMS 30 targets a database (hereinafter, referred to as a source memory database 32) stored in the source memory database area for a data processing request of a user or an application 35. And the processed result is returned to the user or the application 35. The memory DBMS 30 stores the processed data processing request in the log area 32a in the original memory database area. Here, the data processing request is generally made of a structured query language (SQL), but is not limited thereto. Log numbers are sequentially assigned to data processing requests stored in the log area 32a. The log area 32a has a data structure in the form of a queue, so that the size of the allocated memory area can be determined in advance.

The copy unit 38 is a program stored in the auxiliary memory 5 and is loaded into the main memory 4 by a user's operation or the memory DBMS 30 and executed in one process. The replica unit 38 first copies the original memory database 32 and stores it in the copy memory database area of the main memory 4, and initializes the log number storage area 36a allocated to a part of the copy memory database area to zero. do. Subsequently, the replication unit 38 generates a log data request based on the log number stored in the log number storage area 36a, transfers the log data request to the log control unit 37, and transmits the data processing request received from the log transfer unit 37. Reflection in the copy memory database 36 maintains consistency with the original memory database 32. The copy unit 38 then records the log number of the last processed data processing request in the log number storage area 36a.

The log control unit 37 is a program stored in the auxiliary memory 5 and is loaded into the main memory 4 by a user's operation or duplication unit 38 and executed in one process. The log control unit 37 withdraws the data processing request stored in the log area 32a according to the log data request of the replication unit 38 and transfers the data processing request to the replication unit 38.

The operating system (not shown) monitors changes in the copy memory database area and issues system calls (e.g., mmap () 34) to reflect the changed pages to the database 33 stored in the secondary memory 5. Equipped.

Hereinafter, a memory data backup process using the memory database backup apparatus according to the present invention will be described with reference to FIGS. 4 and 5.

First, the memory DBMS 30 loaded and executed in the main memory 4 loads the database 33 stored in the auxiliary memory 5 into the original memory database area of the main memory 4 (S100).

Then, when the user or the memory DBMS 30 executes the replica 38, the replica 38 copies the database 32 stored in the original memory database area and stores it in the copy memory database area of the main memory 4. (S110). This process is described in detail by S200 to S230 of FIG. Referring to FIG. 5, the replication unit 38 checks whether the copy memory database 36 exists in the copy memory database area (S200), and if present, logs stored in the log number storage area 36a in the copy memory database area. Based on the number, a log number performed next is generated (S210). For example, if the log number retrieved from the log number storage area 36a plus 1 is equal to or less than a predetermined value, the log number may be set to that value. If the log number is greater than the predetermined value, the value may be set to 0. Number of logs that can be stored in area 32a). On the other hand, if the copy memory database 36 does not exist in the copy memory database area, the replication unit 38 copies the original memory database 32, stores the data in the copy memory database area of the main memory 4, and initializes it (S220). In step S230, the log number storage area 36a is initialized to zero. By maintaining the log number in the copy memory database area in this manner, the copy memory database 36 can be stored in the original memory without copying the original memory database 32 even when the replica 38 dies and restarts during execution. It can be matched with the database 32.

Referring back to FIG. 4, the memory DBMS 30 processes the data processing request of the user or the application 35 to the source memory database 32 (S120), and does not process any disk I / O related system calls. Regardless of the result, the processed result may be responded to the user or the application 35 (S130). This is because no disk I / O is performed to match the contents of the database 33 on the auxiliary memory 5 with the original memory database 32, which is the object for which the memory DBMS 30 processes the data processing request. Thereafter, the memory DBMS 30 stores the processed data processing request in the log area 32a in the original memory database area (S140).

On the other hand, in response to the log data request of the replication unit 38, the log control unit 37 withdraws the data processing request stored in the log area 32a and transfers it to the replication unit 38 (S150). It will be described in detail by S240, S300, S310, S320, S330. According to FIG. 5, first, the log control unit 37 is loaded into the main memory 4 by the replication unit 38 and executed as one process. When the replication unit 38 sends a log data request including the log number to the log control unit 37 (S240), the log control unit 37 that receives the log number after the log number is stored among the data processing requests stored in the log area 32a. Data processing requests corresponding to the data (ie, log data) are sequentially withdrawn and transmitted to the replica unit (S300 and S310). When there is no log data to be transmitted in the log area 32a, the log control unit 37 periodically monitors the log area 32a and transmits the new log data to the replication unit 38 whenever new log data is generated (S320). ). The replication unit 38 receives log data from the log control unit 37 (S330). Data transmission between the replication unit 38 and the log control unit 37 may be implemented using various types of interprocess communication (IPC).

Referring again to FIG. 4, the copying unit 38 reflects the received data processing request to the copy memory database 36 (S160), which is described in detail by S260, S270, and S280 of FIG. 5. Referring to FIG. 5, the replication unit 38 periodically checks whether there is new log data to be performed while receiving log data from the log control unit 37 (S260). New log data (ie, data processing requests such as SQL) is reflected in the copy memory database 36 to maintain consistency with the original memory database 32 (S270). Next, the copying unit 38 records the log number of the last processed data processing request in the log number storage area 36a to prepare for the case where the copying unit 38 suddenly dies (S280).

Referring back to FIG. 4, system calls, such as mmap () 34, provided in an operating system (not shown) are called by a user or an application program to watch for changes in the copy memory database area to assist in changing pages. It is reflected in the database 33 stored in the memory 5 (S170). At this time, the changes that mmap () checks are not the original memory database 32, but the copy memory database 36, so that the DB core engine 31 processes the data processing request of the user or the application 35. Disk I / O for backup can be performed without disrupting the response of the processed result to the user or application 35.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to the present invention, a copy of a source memory database, which is a target for processing a data processing request of a user or an application on main memory, and a disk I / O related system call processing for matching the contents of a database on disk and a database on disk. By maintaining a memory database and maintaining two separate processes, replication and log control, to maintain consistency among them, the response to database changes can be responded to by real-time applications without being affected by disk I / O for backup. You can get it so quickly that it does not interfere with the operation.

Claims (6)

CPU; Auxiliary memory for storing a database; A main memory for storing a program executed by the CPU and data to be processed; A memory DBMS that loads a database stored in auxiliary memory into an original memory database area of main memory to process a data processing request of a user or an application, and stores the processed data processing request in a log area within the original memory database area; A copy unit for copying a database stored in the original memory database area and storing the copy stored in the copy memory database area of the main memory, and reflecting the data processing request provided by the generation of the log data request to the database stored in the copy memory database area; A log control unit for retrieving a data processing request stored in a log area according to the log data request of the replication unit and transferring the data processing request to the replication unit; And And an operating system having a system call that monitors the change in the copy memory database area and reflects the changed page to the database stored in the auxiliary memory. The memory database backup apparatus of claim 1, wherein the data processing request is made of SQL. The data processing request stored in the log area is given a log number. The copy memory database area is provided with a log number storage area in which log numbers of data processing requests last processed by the replication unit are recorded. And the replication unit generates a log data request based on a log number recorded in a log number storage area. (a) the memory DBMS loading the database stored in the auxiliary memory into the original memory database area of the main memory; (b) copying the database stored in the original memory database area and storing the copy in the copy memory database area of the main memory; (c) the memory DBMS processing a data processing request of a user or an application for a database stored in an original memory database area, and delivering the processing result to the user or application in response; (d) storing, by the memory DBMS, the processed data processing request in a log area in the original memory database area; (e) retrieving the data processing request stored in the log area and forwarding the data processing request stored in the log area according to the log data request of the copying unit; (f) reflecting the transferred data processing request to the database stored in the copy memory database area; And (g) monitoring a change in the copy memory database area by the system call and reflecting the changed page to the database stored in the auxiliary memory. 5. The method of claim 4, wherein the data processing request is made of SQL. The method of claim 4, wherein in step (d) Data processing requests stored in the log area are given a log number. In step (f) In the predetermined area within the copy memory database area, the log number of the data processing request last processed by the copying unit is recorded. In step (e) And the replica unit generates a log data request based on a log number recorded in the copy memory database area.