US20090055444A1 - Method and System for High-Availability Database - Google Patents

Abstract

The present invention provides a system switching function for database management systems which requires no standby resources idling during normal operation. One aspect of the invention is directed to a method for processing databases in a system which includes a plurality of storage areas each storing a database and a plurality of computers each having a database management program running thereon which manages one of the plurality of storage areas. Each storage area is associated with only the computer managing the storage area. The method comprises, when a failure has occurred in one of the plurality of computers as a failed computer, obtaining preset substitution information indicating that the storage area managed by the database management program running on the failed computer is to be managed by the database management program running on another one of the plurality of computers as a substitute computer; and, based on the substitution information, changing association of the storage area with the failed computer to the substitute computer. The storage area is to be managed by the database management program running on the substitute computer.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS
• This application is a continuation of patent application Ser. No. 10/769,351, filed Jan. 30, 2004, which claims priority from Japanese Patent Application No. 2003-115185, filed on Apr. 21, 2003, the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
• The present invention relates to a data processing technique, and more particularly to a technique which is effective when applied to a database management system having a system switching function.
• There is a need for a robust system operating 24 hours a day, every day in the world of Net business in which service interruption could lead to loss of a great business opportunity. What is important with such a system is to localize the influence of a failure when it has occurred and quickly restore the system. To quickly recover from failure, database (DB) systems conventionally use a system switching technique in which a standby system machine is installed in addition to a running system machine for performing service processing, beforehand, and when a failure has occurred in the running system machine, the standby system machine takes over the service processing.
• For example, in literature published by Morgan Kaufmann Publishers in 1993, Jim Gray and Andreas Reuter disclose a hot standby noninterrupted system employing an HA (high availability) system configuration to provide resistance to DB failure. Jim Gray and Andreas Reuter, Morgan Kaufmann Publishers, 1993 “TRANSACTION PROCESSING: CONCEPTS AND TECHNIQUES”, pp. 646-648, pp. 925-927.
• In the literature “Parallel Database Systems: The Future of High Performance Database Systems”, on the other hand, David DeWitt and Jim Gray disclose an architecture (technique) in which the processing load on a database is distributed to a plurality of processors for parallel processing (COMMUNICATIONS OF THE ACM, Vol. 35, No. 6, 1992, pp. 85-98). In the “Shared everything, Shared disk” architecture employed by the above technique, each computer for executing DB processing can access all data, whereas in the “Shared nothing” architecture, each computer can access only the data stored in the disks connected to itself. Parallel Database Systems: The Future of High Performance Database Systems (David DeWitt and Jim Gray, COMMUNICATIONS OF THE ACM, Vol. 35, No. 6, 1992, pp. 85-98)
• The “Shared nothing” architecture is advantageous over the “Shared everything, Shared disk” architecture in that it requires fewer resources to be shared between the components conducting the DB processing and thereby provides higher scalability. The “Shared nothing” architecture also employs a system switching technique in many cases to provide high availability.
BRIEF SUMMARY OF THE INVENTION
• In a system switching method, a standby system machine needs to be set up in addition to a running system machine, as described above, and the standby system machine is in an idle state during normal service operation. It is possible to assign a portion of the ordinary service processing to the standby system machine in a mutual standby configuration. In order to increase the speed at which the systems are switched for restoration, however, a warm standby or hot standby method is often employed in which the standby system is started up to such an extent that it is ready to operate, making it necessary to prepare resources (processes and memory) for the standby system. Systems which require such “standby resources” idling during normal operation are disadvantageous in terms of TCO (Total Cost of Ownership) reduction in system formation and operation since they do not fully utilize their own resources during the normal operation.
• Embodiments of the present invention are directed to solving the above problems. It is, therefore, a feature of the present invention to provide a control method for switching DB systems, which requires no “standby resources” idling during normal operation as described above and exhibits a short system switching time in the case of occurrence of a failure. In particular, a specific embodiment is intended to provide a database processing method which provides high availability for a parallel database management system using the “Shared nothing” architecture.
• A database management system employing the “Shared nothing” architecture stores, beforehand, information on substitution relations between DB servers indicating which one of the DB servers is used as a substitute server if one of the other DB servers has failed. With this arrangement, the database management system receives a query from a user, and if the DB server to which a processing request is to be made is shut down, the database management system determines a substitute DB server based on the above information on the substitution relations between the DB servers and sends the processing request to the determined substitute server instead of the failed DB server. At that time, the database management system adds a substitution instruction to the request. Receiving the above request, the (substitute) DB server determines whether a substitution instruction is attached to the request, and if so, the (substitute) DB server performs data processing in place of the failed server.
• When performing the data processing in place of the failed server, the substitute server switches to the environment of the failed server. If the substitute server previously substituted for the same failed server and has already switched to its environment, no execution environment switching is carried out this time. It is arranged that the database buffer used to access the database for data processing is the same as that used to access the DB storage area associated with the failed server. The database management system may automatically internally generate the above information on the substitution relations between the DB servers indicating which one of the DB servers is used as a substitute server if one of the other DB servers has failed. Furthermore, a plurality of substitute DB servers may be set for each DB server so that they can substitute for the DB server when it has been shut down, and a priority may be given to each substitute server.
• One aspect of the invention is directed to a method for processing databases in a system which includes a plurality of storage areas each storing a database and a plurality of computers each having a database management program running thereon which manages one of the plurality of storage areas. Each storage area is associated with only the computer managing the storage area. The method comprises, when a failure has occurred in one of the plurality of computers as a failed computer, obtaining preset substitution information indicating that the storage area managed by the database management program running on the failed computer is to be managed by the database management program running on another one of the plurality of computers as a substitute computer; and, based on the substitution information, changing association of the storage area with the failed computer to the substitute computer. The storage area is to be managed by the database management program running on the substitute computer.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a diagram showing the general process according to an embodiment of the present invention;
• FIG. 2 is a diagram showing the functional blocks of a database processing system according to an embodiment of the present invention;
• FIG. 3 is a diagram showing a hardware configuration of a computer system according to the embodiment;
• FIG. 4 is a flowchart showing a portion of the processing procedure performed by a processing request control section and a substitution control section F according to the embodiment;
• FIG. 5 is a flowchart showing a portion of the processing procedure performed by a data processing control section and a substitution control section B according to the embodiment;
• FIG. 6 includesFIGS. 6A to 6E which are diagrams each showing an example of substitution information according to the embodiment;
• FIG. 7 includesFIGS. 7A and 7B which are diagrams each showing a configuration of substitute servers according to the embodiment; and
• FIG. 8 includesFIGS. 8A and 8B which are diagrams each showing a configuration of substitute servers according to the embodiment.
DETAILED DESCRIPTION OF THE INVENTION
• Description will be made of a database processing system applied to a database management system employing the “Shared nothing” architecture according to an embodiment of the present invention. This database processing system can immediately resume DB access processing when a failure has occurred (in a running system) without employing any dedicated resources for its standby systems. First, the general process according to an embodiment of the present invention will be briefly described with reference toFIG. 1.
• The database management system (DBMS) of the present embodiment includes a processing request receiving server (or a front end server abbreviated as FES)10 and a DB access server (or a back end server abbreviated as BES)20.
• The processing request receiving server (FES)10 receives aquery50 from a user, analyzes it, generates a DB access request, and sends the DB access request to a DB access server. TheFES10 returns a DB access result to the user as necessary. The DB access server (BES)20, on the other hand, receives the DB access request from the processing request receiving server (FES)10, processes data in a DB storage area according to the request, and returns a result to the processing request receiving server (FES)10 as necessary. The FES10 and the BES20 are each implemented by one or a plurality of processes.
• The database management system of the present embodiment employs the “Shared nothing” architecture, and by use of various methods the database (for example, a table or an index) managed by this system, is divided into a plurality of subtables or subindexes which are each stored in one of a plurality of DB storage areas. Each DB storage area is associated with (controlled by) a predetermined DB access server. Each DB access server only accesses the data (for example, table data or index data) in the DB storage area associated with it. In the example ofFIG. 1, normally, theBES1 only processes access requests to theDB storage area1, while theBES2 only processes access requests to theDB storage area2. The BES1 and the BES2 do not access the same DB storage area.
• Normally, both theBES1 and theBES2 are in operation and therefore all resources (that is, processes and memories implementing the DB access servers) are in use. Then, for example, when a failure has occurred in the power supply, etc., of the information processing apparatus (on which theBES1 is running) and thereby theBES1 has been shut down, another server in operation (in this example, the BES2) takes over the processing to continue the service. That is, theBES2 processes the DB access request made to theBES1.
• Specifically, receiving thequery request50 from a user (application program), theFES10 analyzes the query request to determine the DB storage area that stores the data to be accessed. If the DB access server designated to access the determined DB storage area is shut down, theFES10 determines which DB access server will be a substitute server based on substitution information for failed servers atstep13. In this example, theBES2 is determined to be the substitute server. TheFES10 then adds a substitution instruction to aDB access request40 atstep14 and transmits the request to the DBaccess server BES2 atstep15. The substitution instruction may be a flag or an identifier identifying theBES1. This example uses a flag.
• Receiving theDB access request40 from the FES10 (step21), the DBaccess server BES2 determines whether the DB access request is for theDB storage area2 managed by theBES2 itself or another DB storage area atstep22. This determination is made based on the value of the substitution instruction (flag). If the substitution instruction flag is set to ON, the DBaccess server BES2 recognizes from the substitution information for failed servers that the access request is for theDB storage area1 originally managed by theBES1. The DBaccess server BES2 obtains the substitution information for the failedservers30 which is stored in astorage device4 such as a hard disk device atstep23, and switches to the execution environment of the DBaccess server BES1 atstep24. For example, the environment variables and memory information of the process implementing the DBaccess server BES2 are replaced with those for the DBaccess server BES1.
• The DBaccess server BES2 performs DB access processing in the new execution environment atstep25 to access theDB storage area1 and manipulates data according to the request. In this example, the DBaccess server BES2 transmits to theFES10 the table data62 (that is, a value of12) stored in the DB storage area1 (61) in thedatabase60 as the execution result. Receiving the table data, theFES10 returns it to the user.
• In this example, it is assumed that the substitution information for failedservers30 is stored in the DBMS by a user such as a manager of the DBMS beforehand. However, the DBMS may automatically internally generate this information, making it possible to reduce the burden on the manager.
• Thus, the DBaccess server BES2 processes an access request to theDB storage area1 in place of the DBaccess server BES1 when a failure has occurred in the DBaccess server BES1. Such a server is referred to as a substitute server in this specification. When a DB access server BES works as a substitute server and performs processing, the BES process is not changed for substitute server processing, eliminating the need for generating an extra process.
• As described above, a substitute server for each server may be registered or determined beforehand. With this arrangement, when a failure has occurred in a BES, the FES detects the failed BES, and by use of a substitution instruction, the FES instructs the substitute server in operation to perform processing in place of the failed BES, making it possible to immediately resume the DB access processing when a failure has occurred without employing any dedicated resources for the standby system.
• In this example, the FES and the BESs are each installed on a different information processing apparatus. However, they may be set up on the same information processing apparatus, making it possible to efficiently use the hardware resources. Furthermore, the functions of the FES and the BES of the present embodiment may be implemented as those of a single DB server, making it unnecessary for the manager of the database management system to handle the FES and the BES separately, thereby reducing the management cost.
• FIG. 2 schematically shows the configuration of a database management system according to the present embodiment.FIG. 2 showsapplication programs6 created by users and adatabase management system2 for managing the entire database system including queries and resources. Thedatabase management system2 includes a processing request receiving server (or a front end server abbreviated as FES)10 and a DB access server (or a back end server abbreviated as BES)20. Thedatabase management system2 further includes adata buffer230 and has adatabase3 for permanently or temporarily storing data to be accessed, and substitution information for failedservers30.
• The processing request receiving server (FES)10 receives a query from anapplication program6, analyzes it, generates a DB access request, and sends the DB access request to a DB access server. The processing request receiving server (FES)10 returns a DB access result to theapplication program6 as necessary. The DB access server (BES)20 receives the DB access request from the processingrequest receiving server10 and accesses thedatabase3 stored in an external storage apparatus through thedatabase buffer230. In the above example ofFIG. 1, the substitute server (the BES2) uses the database buffer used by the failed original BES (1) to perform DB access processing. That is, the failed original BES and the substitute server (BES) share the database buffer.
• The abovedatabase management system2 is connected to other systems through a network. It should be noted that the processing request receiving server (FES)10 and the DB access server (BES)20 may not necessarily be set up on the same information processing apparatus. They may be each installed on a different information processing apparatus and connected to each other through a network, functioning as a single database management system. Further, the database management system may include a plurality of FESs to distribute requests received from a large number of users. Still further, the database management system may include a plurality of BESs, making it possible to increase the level of parallel operation on data and perform data processing on even a large-scale database at high speed.
• The processingrequest receiving server10 includes a processingrequest control section211 for performing syntax analysis and semantic analysis of a query, determining an appropriate processing procedure, generating code according to the processing procedure, and making a DB access request to theDB access server20. The processingrequest receiving server10 also includes a substitutioncontrol section F212 for, when the processingrequest control section211 makes a DB access request, determining the operational state of the target DB access server to which the request is to be sent, changing the target DB access server as necessary (at step213), and instructing the new target DB access server to substitute for the original target DB access server (at step214).
• TheDB access server20 includes a dataprocessing control section221 for performing access control of data in thedatabase3 according to a DB access request (generated code) received from the processingrequest receiving server10. TheDB access server20 also includes a substitutioncontrol section B222 for, when the dataprocessing control section221 has received the DB access request, determining whether the request indicates that substitution is required, and switching to the necessary execution environment for the substitute server (at step223). The substitution control section B has a function to control restoration of the data and transaction for the failed server. Specifically, when a failure has occurred in a server (original server), the substitution control section B (in the substitute server) restores the DB storage area, etc., for the original server and cancels the current ongoing processing so as to be able to restore the transaction.
• FIG. 3 is a diagram showing a hardware configuration of a computer system according to the present embodiment. This computer system includesinformation processing apparatuses3000,3100, and3200.
• Theinformation processing apparatus3000 is made up of aCPU3002, amain memory3001, acommunications control apparatus3003, an I/O control apparatus3004, and aterminal3006. An application program3008 executed by theCPU3002 runs on themain memory3001. When the application program3008 has sent theuser query50 to the processingrequest receiving server10 of theDBMS2, the query request (the sent user query) goes through thecommunications control apparatus3003 of theinformation processing apparatus3000, anetwork3007, and thecommunications control apparatus3003 of theinformation processing apparatus3100 before reaching the processingrequest receiving server10.
• Theinformation processing apparatus3100 is made up of aCPU3002, amain memory3001, acommunications control apparatus3003, an I/O control apparatus3004, external storage apparatuses3005 (magnetic disk drives, etc.), and aterminal3006. Thedatabase management system2 including the processingrequest receiving server10, described above with reference toFIG. 2, is executed by theCPU3002 and runs on themain memory3001 in theinformation processing apparatus3100. Anexternal storage apparatus3005 stores thedatabase3 managed by thedatabase management system2. Aprogram3101 implementing thedatabase management system2 is stored in anotherexternal storage apparatus3005. The processingrequest receiving server10 writes/reads data to/from theexternal storage apparatuses3005 through the I/O control apparatus3004 and exchanges data with other information processing apparatuses connected to the processingrequest receiving server10 through thecommunications control apparatus3003 and thenetwork3007.
• Theinformation processing apparatus3200 is made up of aCPU3002, amain memory3001, acommunications control apparatus3003, an I/O control apparatus3004, external storage apparatuses3005 (magnetic disk drives, etc.) and aterminal3006. Thedatabase management system2 including theDB access server20, described above with reference toFIG. 2, is executed by theCPU3002 and runs on themain memory3001 in theinformation processing apparatus3200. Anexternal storage apparatus3005 stores thedatabase3 managed by thedatabase management system2. Aprogram3101 implementing thedatabase management system2 is stored in anotherexternal storage apparatus3005. TheDB access server20 writes/reads data to/from theexternal storage apparatuses3005 through the I/O control apparatus3004 and exchanges data with other information processing apparatuses connected to theDB access server20 through thecommunications control apparatus3003 and thenetwork3007.
• Theexternal storage apparatuses3005 each storing adatabase3 associated with (managed by) one of the twoinformation processing apparatuses3200 are shared disks and can be accessed by other information processing apparatuses. Clusterware or the like that controls the normal operation and the switchover operation of thedatabase management system2 performs access control to the above shared disks.
• FIG. 4 is a flowchart showing a portion of the processing procedure performed by the processing request control section and the substitution control section F according to the present embodiment.
• First of all,step401 receives a query from a user, and based on information obtained as a result of analyzing the query from the user,step402 determines the DB access server designated to access the DB storage area used for executing the query. Then, step403 determines whether the determined DB access server is in operation. If it is in operation, the processing proceeds to step407 which transmits a processing request to the determined DB access server.
• If, on the other hand, the DB access server has been shut down and therefore is not in operation, the processing proceeds to step404 which obtains the substitution information for failedservers30 concerning the failed DB access server. Then, step405 determines a substitute server based on the obtained substitution information for failedservers30. Step406 adds a substitution instruction to a processing request, that is, sets the substitution instruction flag to ON. After that, the processing proceeds to step407 which transmits the processing request to the substitute DB access server.
• FIG. 5 is a flowchart showing a portion of the processing procedure performed by the data processing control section and the substitution control section B according to the present embodiment. The DB access processing below is performed after the transmission of a processing request illustrated by the flowchart ofFIG. 4.
• First,step501 receives an execution request from the FES, and step502 determines whether the received execution request indicates that substitution is required. If the substitution instruction flag is set to ON, the processing proceeds to step503 which obtains the substitution information for failedservers30 to check for the server (failed server) to be substituted for by this DB access server. Step504 obtains the name of the server to be substituted for from the obtained substitution information for failedservers30 and switches to the execution environment of the server. Step505 performs DB access processing in the new execution environment, accessing the DB storage area assigned to the failed DB access server in place of the server to manipulate data.
• If, on the other hand, the substitution instruction flag is set to OFF atstep502, no execution environment switching operation is carried out, and step505 accesses the DB storage area assigned to this server to manipulate data.
• Step504 may check the current execution environment and may not switch execution environments when the BES (this BES) which is to process the processing request is the currently running BES. Furthermore, atstep505, this BES may return to its original execution environment after the DB access processing has been performed. The above steps may be optimally controlled by a balancer or a scheduler for controlling the processing request.
• FIG. 6 includesFIGS. 6A to 6E which are diagrams each showing an example of the substitution information according to the present embodiment. In the example ofFIG. 6A, the substitution information for failedservers30 includes the server name of each DB access server and the server name of the substitute server for each DB access server. When a DB access server has failed, the substitute server accesses the DB storage area assigned to the failed DB access server in place of the failed DB access server. Asubstitution information entry600 indicates that when the DBaccess server BES1 has been shut down due to a failure, theBES2 takes over the processing as a substitute server.
• FIG. 7 includesFIGS. 7A and 7B which are diagrams showing configurations of substitute servers corresponding toFIGS. 6B and 6C, respectively, whileFIG. 8 includes8A and8B which are diagrams showing configurations of substitute servers corresponding toFIGS. 6D and 6E, respectively.
• The substitution information shown inFIG. 6B corresponds to the configuration of substitute servers shown inFIG. 7A.Substitution information entries601 and602 inFIG. 6C indicate that a DB access server BES3 (705) on theinformation processing apparatus701 and a DB access server BES4 (706) on theinformation processing apparatus702 are set as each other's substitute servers. That is, they are in a mutual substitution configuration. Specifically, when theBES3 has been shut down, theBES4 takes over the processing from the BES3 (as indicated by the substitution information601). When theBES4 has been shut down, on the other hand, theBES3 takes over the processing from the BES4 (as indicated by the substitution information602).
• Further, the BES5 and theBES6 on theinformation processing apparatus703 and the BES7 and the BES8 on theinformation processing apparatus704 are also in a mutual substitution configuration. Specifically, when the BES5 has been shut down, the BES7 takes over the processing from the BES5, and when theBES6 has been shut down, the BES8 takes over the processing from theBES6. On the other hand, when the BES7 has been shut down, the BES5 takes over the processing from the BES7, and when the BES8 has been shut down, theBES6 takes over the processing from theBES6.
• The notational convention used byFIGS. 7 and 8 will be described with examples. InFIG. 7A, the parentheses “(“and”)” in the indication “(BES4*)” in theDB server705 indicates that the DB server is not operating as theBES4, that is, the DB server does not access the DBstorage area RD4 for the current DB processing (it is operating as the BES3). Further, the asterisk “*” in the same indication indicates that theDB server705 is designated as the substitute server for the server to which the asterisk “*” is attached (that is, BES4).
• FIG. 7A shows the following operational states of servers. A failure has occurred in theinformation processing apparatuses701 and703, and as a result theBES3, BES5, andBES6 have been shut down. A request for data manipulation requiring access to the DBstorage area RD3 is transmitted to theDB access server706 after a substitution instruction is attached to it. Receiving the request, the process implementing theDB access server706 performs the processing as theBES3, accessing theRD3.
• A request for data manipulation requiring access to the RD5 is transmitted to theDB access server709 after a substitution instruction is attached to it. Receiving the request, the process implementing theDB access server709 performs the processing as the BES5, accessing the RD5.
• The substitution information shown inFIG. 6C corresponds to the configuration of substitute servers shown inFIG. 7B.Substitution information entries607,608, and609 inFIG. 6C indicate that a DB access server BES9 (715) on aninformation processing apparatus712, a DB access server BES10 (716) on aninformation processing apparatus713, and a DB access server BES11 (717) on aninformation processing apparatus714 are set as one another's substitute servers. That is, they are in a unidirectional ring substitution configuration. Specifically, when the BES9 has been shut down, theBES10 takes over the processing from the BES9 (as indicated by the substitution information607). When theBES10 has been shut down, on the other hand, theBES11 takes over the processing from the BES10 (as indicated by the substitution information608). Further, when theBES11 has been shut down, the BES9 takes over the processing from the BES11 (as indicated by the substitution information609).
• FIG. 7B shows the following operational states of servers. A failure has occurred in theinformation processing apparatus712, and as a result the BES9 has been shut down. A request for data manipulation requiring access to the DB storage area RD9 is transmitted to theDB access server716 after a substitution instruction is attached to it. Receiving the request, the process implementing theDB access server716 performs processing as the BES9, accessing the RD9.
• The substitution information shown inFIG. 6D corresponds to the configuration of substitute servers shown inFIG. 8A.Substitution information entries610,611, and612 inFIG. 6D indicate the substitute servers for a DB access server BES12 (804) on aninformation processing apparatus801, a DB access server BES13 (805) on aninformation processing apparatus802, and a DB access server BES14 (806) on aninformation processing apparatus803. In particular, thesubstitution information entries611 and612 indicate that theBES12 is set as the substitute server for both theBES13 and theBES14. That is, they are in an n:1 substitution configuration, where n is 2 in the above example.
• FIG. 8A shows the following operational states of servers. A failure has occurred in theinformation processing apparatus803, and as a result theBES14 has been shut down. A request for data manipulation requiring access to the DBstorage area RD14 is transmitted to theDB access server804 after a substitution instruction is attached to it. Receiving the request, the process implementing theDB access server804 performs processing as theBES14, accessing theRD14.
• The substitution information shown inFIG. 6E corresponds to the configuration of substitute servers shown inFIG. 8B.Substitution information entries613,614, and615 inFIG. 6E indicate that DB access servers BES16 (813), BES17 (814), and BES18 (815) are set as the substitute servers for a DB access server BES15 (812) on aninformation processing apparatus808. When theBES15 has been shut down, the substitute server for theBES15 is determined based on the values of the substitution priority order entries in the substitution information. That is, these DB access servers are in an n-stage substitution configuration.
• The actual substitution server for theBES15 is determined as follows. First of all, the BES16, indicated by thesubstitution information613, is designated as the substitute server (candidate). If the BES16 also has been shut down, the BES17, indicated by thesubstitution information614, is set as the substitute server (candidate) according to the substitution priority order. Further, if the BES17 also has been shut down, the BES18 is set as the substitution server.
• FIG. 8B shows the following operational states of servers. A failure has occurred in theinformation processing apparatus808, and as a result theBES15 has been shut down. Furthermore, another failure has occurred in theinformation processing apparatus809, and as a result the BES16 also has been shut down. A request for data manipulation requiring access to the DBstorage area RD15 is transmitted to theDB access server814 after a substitution instruction is attached to it according to thesubstitution information614. Receiving the request, the process implementing theDB access server814 performs processing as theBES15, accessing theRD15.
• The above processing illustrated by the flowcharts inFIGS. 4 and 5 is executed by programs running on the computer system shown inFIG. 3. In some embodiments, the programs may not be stored in external storage apparatuses directly and physically connected to the computer system, unlike the example ofFIG. 3. Instead, the programs may be stored on computer-readable/writable storage media such as hard disk drives and flexible disk drives. Furthermore, they may be stored in external storage apparatuses connected to a different information processing apparatus which is connected through a network to an information processing apparatus constituting the computer system shown inFIG. 3.
• Embodiments of the present invention can provide a method and system for processing a database, capable of quickly resuming DB processing service in the case of occurrence of a failure without employing any “standby resources” idling during normal operation in a database management system using the “Shared nothing” architecture.
• The above-described arrangements of apparatus and methods are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims (11)

1-3. (canceled)

4. A method for processing databases in a system comprising a processing request server, a plurality of storage areas, and a plurality of database access servers, wherein each storage area in the plurality of storage areas includes at least one database, wherein each database access server in the plurality of database access servers is associated with a storage area from among the plurality of storage areas thereby enabling said each database access server to manage and access its associated storage area, the method comprising:

when a failure has occurred in a first database access server from among the plurality of database access servers, then obtaining preconfigured substitution information including a mapping between the first database access server and a second database server from among the plurality of database access servers, wherein the first database access server is different from the second database server;

based on the mapping, re-associating a first storage area associated with the first database access server such that the first storage area becomes associated the second database access server thereby enabling the second database access server to manage and access the first storage area;

receiving at the processing request server a processing request directed to the first database access server;

determining if the first database access server is in operation;

if the first database access server is in operation, then forwarding the processing request to the first database access server, wherein the first database access server is configured to process the forwarded processing request;

if the first database access server is not in operation, then:

identifying the second database access server as a substitute for the first database access server based on the preconfigured substitution information; and

transmitting another processing request to the second database access server, wherein the second database access server is configured to receive said another processing request, obtain execution environment information for the first database access server, switch an execution environment of the second database access server to that of the first database access server based on the execution environment information, process said another processing request on behalf of the first database access server, and return to an original execution environment of the second database access server after completion of processing said another processing request.

5. The method ofclaim 4, wherein the mapping associates an identifier of the first database access server with an identifier of the second database access server, the mapping indicating that the storage area associated with the first database access server is to be associated with the second database access server when a failure occurs in the first database access server.

6. The method ofclaim 5, wherein the mapping further indicates that a storage area associated with second database access server is to be associated with the first database access server when a failure occurs in the second database access server.

7. The method as recited inclaim 4, wherein the preconfigured substitution information comprises a substitution configuration in which a group of database access servers from the first database access server to a last database access server are associated with each other such that the first database access server is to manage a storage area for the second database access server, the second database access server is to manage a storage area for a third database access server, and the last database access server is to manage a storage area for the first database access server.

8. The method as recited inclaim 4, wherein the preconfigured substitution information comprises an n-to-1 substitution configuration whereby one database access server is to manage storage areas for n other database access servers.

9. A system for processing databases, the system comprising:

a processing request receiving server;

a plurality of storage areas, each storage area including at least one database; and

a plurality of database access servers, each database access server being associated with a storage area in the plurality of storage areas, thereby enabling said each database access server to manage and access its associated storage area,

wherein the processing request receiving server is configured to:

receive a processing request directed to a first database access server in the plurality of database access servers;

determine whether the first database access server is in operation;

forward the processing request to the first database access server, wherein the first database access server is configured to process the forwarded processing request when the first database access server is in operation; and

when the first database access server is not in operation:

obtain preconfigured substitution information including a mapping between the first database access server and a second database access server in the plurality of database access servers;

identify the second database access server as a substitute for the first database access server based on the preconfigured substitution information;

transmit another processing request to the second database access server, wherein the second database access server is configured to receive said another processing request, obtain execution environment information for the first database access server, switch an execution environment of the second database access server to that of the first database access server based on the execution environment information, process said another processing request on behalf of the first database access server, and return to an original execution environment of the second database access server after completion of processing said another processing request.

10. The system as recited inclaim 9, wherein the preconfigured substitution information comprises a substitution configuration in which a group of database access servers from the first database access server to a last database access server are associated with each other such that the first database access server is to manage a storage area for the second database access server, the second database access server is to manage a storage area for a third database access server, and the last database access server is to manage a storage area for the first database access server.

11. The system as recited inclaim 9, wherein the preconfigured substitution information comprises an n-to-1 substitution configuration whereby one database access server is to manage storage areas for n other database access servers.

12. The system ofclaim 9, wherein the mapping associates an identifier of the first database access server with an identifier of the second database access server, the mapping indicating that a storage area associated with the first database access server is to be associated with the second database access server when a failure occurs in the first database access server.

13. The system ofclaim 9, wherein the preconfigured substitution information includes a plurality of mappings between database access servers, each mapping including priority information indicating a priority of said each mapping with respect to other mappings.

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