JP5621465B2 - Database system - Google Patents

Description

  The present invention relates to a database system.

  The memory database operates faster than the disk database, but data is lost when a failure occurs. As a countermeasure for this, it is common to adopt a configuration in which a log is created when the memory database is updated and the log is reflected in the back-end disk database as needed (delayed update).

  As a technique for creating a replica of a database, for example, Patent Document 1 discloses that a master database to be updated, a replica that stores a replica of the master database, and a master database update data on the replica, a specific database table, priority Precedence to update any one of the table items and the priority key, and a predetermined priority to update specific update data having a high priority before update data having a low priority A priority information storage unit that holds priority information indicating the order, and updates and reads update data according to the priority information so that update data with high priority is extracted earlier than update data with low priority A distribution unit that extracts data and a management unit that updates the replica with the extracted update data Over database system is disclosed.

Japanese Patent No. 3686564

  In a system that requires high availability, if the front database becomes unavailable for some reason, the back end database will temporarily function as the front side. When reflected in the end database, it takes time, and there is a problem that the service cannot be provided during that time.

  In the system disclosed in Patent Document 1, data is reflected in the replica according to the specified priority. However, when the front database becomes unavailable, the service stop time during switching to the back end database is reduced. It cannot cope with shortening.

  Accordingly, an object of the present invention is to provide a database system capable of minimizing the service stop time associated with switching while reflecting the minimum necessary information in the switching destination database when switching the database. It is.

  The database system according to the present invention manages a main database holding data reflecting data update processing requested by an application, log data of the data update processing for the main database, and reflects the log data in a sub-database as needed And an update log management unit that manages the log data separately for log data of a process that needs to maintain a processing order and log data of a process that does not need to maintain the order, When the main database becomes unusable, after reflecting all the log data of the processing that needs to maintain the processing order in the sub-database, the data update processing from the application is directly reflected in the sub-database. It is what makes it possible.

  According to the present invention, when a database is switched, the minimum required information is reflected in the switching destination database, and the service stop time associated with the switching can be minimized.

The block diagram which shows the structure of the database system by embodiment of this invention. The flowchart of operation | movement of a memory database by embodiment of this invention. The figure explaining the function of the update log management part by embodiment of this invention. The figure which shows the structural example of the update log management table by embodiment of this invention. It is a figure which shows the example of a correspondence definition of memory database operation and disk database operation by embodiment of this invention. The flowchart of the process at the time of database switching by embodiment of this invention. The flowchart of the process of an access control part at the time of database switching by embodiment of this invention.

Next, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a database system 1 according to an embodiment of the present invention. As shown in the figure, the database system 1 includes an application unit 101, an access control unit 102, a memory database 103, an update log management unit 104, a memory / disk DB operation conversion unit 105, and a disk database 106.

  As the database system 1, a dedicated or general-purpose computer including a CPU, a memory such as a ROM or a RAM, an external storage device that stores various information, an input interface, an output interface, a communication interface, and a bus connecting them can be applied. . The database system 1 may be configured by a single computer or may be configured by a plurality of computers connected to each other via a communication network.

  The application unit 101, the access control unit 102, the update log management unit 104, and the memory / disk DB operation conversion unit 105 correspond to modules of functions realized when the CPU executes a predetermined program stored in a ROM or the like. . The memory database 103 is realized by a memory such as a RAM. The disk database 106 is realized by an external storage device such as a hard disk.

Next, the operation of the database system 1 will be described.
First, a normal operation, that is, an operation when the memory database 103 is usable will be described.

  The application unit 101 accesses the memory database 103 or the disk database 106 via the access control unit 102, and refers to or updates data stored in the database.

  When the data update process is performed, the application unit 101 adds the information at the time of access if the update contents need to maintain the order. The application unit 101 determines whether or not it is necessary to maintain the order. For example, if the data content is information that should not be inconsistent, such as deposit / withdrawal information, it is determined that the order must be maintained, and the information is not necessarily required for continuation of the service by the database system, such as data reference or batch processing. Determines that it is not necessary to maintain order.

  The access control unit 102 transfers access from the application unit 101 to the memory database 103.

The operation of the memory database 103 will be described with reference to the flowchart of FIG.
When receiving an access from the application unit 101 (step S11), the memory database 103 determines whether or not the processing content is a data update request (step S12). If it is determined in step S12 that the request is a data update request (Yes), the process proceeds to step S13. If it is not a data update request (No), the process proceeds to step S14 and data is returned.

  In step S13, the update data of the target data stored in the application unit 101 is updated. Further, in step S15, it is determined whether or not the data update process requires order retention. If the update process requires order retention (Yes), the process advances to step S16 to notify the update log management unit 104 of the update contents together with the necessity of order retention. If the update process does not require maintaining the order (No), the process proceeds to step S17, and the update content is notified to the update log management unit 104.

  The update log management unit 104 stores the update content notified from the memory database 103 in the update log management table. As shown in FIG. 3, the update log management unit 104 has an update log management table that records the contents updated in the memory database 103. As the update log management table, an update log table that needs to maintain order and an update log table that does not need to maintain order are prepared.

  FIG. 4 is a diagram illustrating a configuration example of the update log management table. The update log management table records the time when the memory database 103 was updated, the update operation type (write, delete, etc.), the key type of the updated record, the content of the updated record, and the like.

  The database system 1 performs a delayed update in which a log of update contents of the memory database 103 is reflected in the disk database. At the time of delayed update, the update log management unit 104 sets the memory / disk DB operation conversion unit 105 to the data in each update log management table in order from the oldest update time at an appropriate timing, such as when the system load is low. Through the disk database 106. At this time, the necessity of maintaining the order of the update logs is not distinguished. In addition, the log that has been reflected in the disk database 106 is deleted from the update log management table.

  The memory / disk DB operation conversion unit 105 converts an operation executed in the memory database 103 into a process corresponding to the disk database 106. FIG. 5 shows an example of definition information of instructions for the disk database 106, such as instructions for the memory database 103 and corresponding SQL. The memory / disk DB operation conversion unit 105 converts accesses from the application unit 101 and the update log management unit 104 into operations for the disk database 106 according to the definition information.

  The disk database 106 receives delayed update information from the update log management unit 104 input via the memory / disk DB operation conversion unit 105, and receives a data update / reference request from the application unit 101 when the memory database 103 is stopped. Update and return data.

  The access control unit 102 transfers the access from the application unit 101 to the disk database 106 via the memory / disk DB operation conversion unit 105. For this reason, the application unit 101 is not made aware of which database is being accessed.

  Next, an operation when the memory database 103 becomes unusable will be described with reference to FIGS.

  When the memory database 103 becomes unusable due to a failure or the like, as shown in FIG. 6, the update log management unit 104 first reflects all the logs of the update log table with the required order on the disk database 106. When the reflection is completed, a reflection completion notification is transmitted to the access control unit 102. The log data remaining in the normal update log table is reflected in the disk database 106 as needed at an appropriate timing. These update log reflection processes are also performed through the memory / disk DB operation conversion unit 105.

  Further, as shown in FIG. 7, when the access of the application unit 101 is detected (step S21), the access control unit 102 determines whether or not the memory database 103 is accessible (step S22).

  If the memory database 103 is accessible (Yes), the processing request is transferred to the memory database 103 (step S23). On the other hand, when the memory database 103 cannot be accessed (No), it is determined whether or not the processing content is access to data that requires order (step S24).

  If it is determined in step S24 that the access is not to data that requires order (No), the processing request is transferred to the disk database 106 via the memory / disk DB operation conversion unit 105 (step S26).

  On the other hand, if it is determined in step S24 that the access is to data that requires order (Yes), whether or not the update update manager 104 has received the notification of completion of reflection of the required order update log has been received. Is determined (step S25).

  If the reflection completion notification has been received (step S25; Yes), the processing request is transferred to the disk database 106 via the memory / disk DB operation conversion unit 105 (step S26). If the reflection completion notification has not been received (step S25; No), the transfer to the disk database 106 is suspended, and the transfer is started upon receipt of the reflection completion notification.

  As described above, according to the present embodiment, update log data for the memory database 103 is managed separately for processing that requires ordering and processing that does not need to be performed, and the memory database 103 cannot be used, and the application unit 101 can access it. When the database to be switched is switched to the disk database 106, only the update log data that requires ordering is reflected in the disk database 106, and access to the disk database 106 of the application unit 101 is permitted. For this reason, at the time of database switching, the minimum required information is reflected in the switching destination disk database 106, and the service stop time associated with switching can be minimized.

  In addition, the update log for the memory database 103 is further provided with a reflection priority (high, medium, low, etc.), and when the database is switched, for example, when all the high priority logs are reflected, the service is restarted. You may make it reflect sequentially in order of low to moderate.

  The present invention is suitable for a system that performs a delayed update on a back-end database and wants to shorten the service stop time associated with the switching as much as possible when the database is switched due to a failure or the like.

A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited thereto.
(Supplementary note 1) a main database that holds data reflecting data update processing requested by an application;
An update log management unit for managing log data of the data update process for the main database and reflecting the log data in a sub-database as needed,
The update log management unit
The log data is managed separately into log data for processes that need to maintain the processing order and log data for processes that do not need to be stored. When the main database becomes unavailable, the processing order must be maintained. A database system that makes it possible to directly reflect data update processing from the application to the sub-database after reflecting all log data of various processes in the sub-database.

(Supplementary Note 2) The update log management unit
The reflection priority of each log data is managed, and at the time of switching from the main database to the sub database, the log data to which a predetermined reflection priority is assigned is reflected in the sub database, and then the application The database system according to supplementary note 1, which makes it possible to directly reflect data update processing from the sub-database.

  DESCRIPTION OF SYMBOLS 1 Database system, 101 Application part, 102 Access control part, 103 Memory database, 104 Update log management part, 105 Memory / disk DB operation conversion part, 106 Disk database

Claims (2)

A main database that holds data reflecting the data update process requested by the application;
An update log management unit for managing log data of the data update process for the main database and reflecting the log data in a sub-database as needed,
The update log management unit
The log data is managed separately into log data for processes that need to maintain the processing order and log data for processes that do not need to be stored. When the main database becomes unavailable, the processing order must be maintained. A database system that makes it possible to directly reflect data update processing from the application to the sub-database after reflecting all log data of various processes in the sub-database. The update log management unit
The reflection priority of each log data is managed, and at the time of switching from the main database to the sub database, the log data to which a predetermined reflection priority is assigned is reflected in the sub database, and then the application The database system according to claim 1, wherein the data update processing from the server can be directly reflected in the sub-database.