Database remote replication for multi-tier computer systems by homayoun yousefi'zadeh

• US 20040030739A1
• Filed: 08/06/2002
• Published: 02/12/2004
• Est. Priority Date: 08/06/2002
• Status: Active Grant

• Current Assignee: Yousefiʼzadeh, Homayoun
• Original Assignee: Yousefiʼzadeh, Homayoun
• Inventors: Yousefiʼzadeh, Homayoun
• Granted Patent: US 7,370,064 B2
• Time in Patent Office: Days
• US Class Current: 709/201
• CPC Class Codes: G06F 11/202 where processing functionality is redundant redundant communication control functionality G06F11/2005, redundant storage control functionality G06F11/2089
• CPC Class Codes: G06F 11/2056 by mirroring
• CPC Class Codes: G06F 16/2471 Distributed queries

Abstract

A replication method and system for a computer system having multiple database servers for at least one database, wherein database servers are provided with a unified view of the data content. The method includes the steps of establishing connections to said multiple database servers for communicating with said database servers; distinguishing between read and update query requests; and assigning queries to respective ones of said multiple database servers to preserve the consistency of the respective unified view of data of said multiple database servers in case of receiving update queries. Assigning each new query includes the steps of distinguishing between read and update queries, determining possible assignments of that new query to one or more of said multiple database servers, each said possible update query assignment to one of said multiple database servers being based on a transaction-based replication scheme to preserve the unified view data of said multiple database servers; and assigning that new query to one of said multiple database servers as a function of said possible assignments of that new query, to preserve respective unified view of data of said multiple database servers.

Claims

1. A remote replication method for a computer system including multiple database servers for at least one database server.

3. The method of claim 1, wherein step of assigning each new update query comprises the steps of:

(i) placing transaction locks on the portion of data requested by the update queries;

(ii) synchronizing the update query among the database servers and hence preserving the unified view of data among said database servers; and

(iii) removing the transaction locks as the result of one of the following two events;

synchronizing all and each of database servers according to the update query change OR rolling back the update query change for those databases successfully inserted the change as the result of rest of database servers failing to insert the change.

4. The method of claim 1, further either fully replicates the data content among said database servers or provides means of consistency for said database systems to access the common data content.

5. The method of claim 1, further monitors the health status of all of the existing database servers and isolates any database server that is not responding from the rest of database servers.

6. The method of claim 1, further synchronizes the view of data of a newly added database with the unified view of data of said database servers prior to bringing the newly added database online wherein the synchronization procedure introduces no interruption of service in the operation of said computer system and comprises steps of:

(i) creating frequent synchronized checkpoints in the said database servers

(ii) maintaining a transient recovery change log of intermediate update query requests in all periods of having an active synchronization procedure.

(iii) Synchronizing the newly added database to the most recent synchronized checkpoint

(iv) Applying the remote replication method change log entries after synchronizing the newly added database with the most recent synchronized checkpoint of said database systems

(v) Finding a point in time containing no transaction in progress and bringing the newly added database server online.

7. The method of claim 1, further includes the logical step of establishing connections to said multiple database servers using TCP/IP protocols for known IP addresses and port numbers, maintaining said connections to said database servers, and reusing existing connections for communication with said database servers.

8. The method of claim 7, wherein the step of establishing connections further includes the steps of:

(i) establishing a first set of connections to a first subset of said multiple database servers using a first interface; and

(ii) establishing a second set of connections to a second subset of said multiple database servers using a second interface; and

(iii) the step of assigning queries further includes the steps of, for each of said subsets of the multiple database servers;

assigning each of one or more queries to respective ones of database servers in that subset of multiple database servers.

9. The method of claim 8, further comprising the steps of, after processing of the new query request in said database, receiving response from the database in relation to said new query request via the selected database sever, and communicating the response for delivery directly to the requester from the database server.

10. The method of claim 8, wherein one or more of said processes comprise object oriented technologies with the steps of utilizing a single-threaded or a multi-threaded inter-process communication protocol.

12. The remote replication system of claim 11, wherein the remote replication method further comprises all of said characteristics of claims 2 through 10.

23. The computing system of claim 28, wherein the remote replication system further comprises all of said characteristics of claims 12 through 16.

26. The database computing system of computer program product of claim 25, further comprises all of said characteristics of claims 23 and 24.

2. The method of claim, wherein the database servers are provided with a unified view of data, comprising the steps of:

(i) receiving one or more query requests (queries) including database functions for operating on the data stored in said database servers;

(ii) distinguishing between read and update queries for said query requests;

(iii) establishing connections to said multiple database servers for communicating with said database servers; and

(iv) preserving unified view of data among said database servers after receiving update queries that change database servers data content.

11. A remote replication system with a remote replication method for a computer system comprising multiple database servers for at least one database server,

(i) At least one remote replication server for receiving new query requests including database functions for operating on the data stored in said database servers and providing said database servers with a unified view of data by keeping said database servers contents synchronized;

(ii) At least one database server interface including connections for communication with said multiple database servers to send each new query to one of said multiple database servers.

13. The remote replication system of claim 11, further synchronizes the view of data of a newly added database with the unified view of data of said database servers prior to bringing the newly added database online wherein the synchronization procedure introduces no interruption of service in the operation of said computer system and comprises steps of:

(i) creating frequent synchronized checkpoints in the said database servers

(ii) maintaining a transient recovery change log of intermediate update query requests in all periods of having an active synchronization procedure

(iii) Synchronizing the newly added database to the most recent synchronized checkpoint

(iv) Applying the remote replication method change log entries after synchronizing the newly added database with the most recent synchronized checkpoint of said database systems

(v) Finding a point in time containing no transaction in progress and bringing the newly added database server online.

14. The remote replication system of claim 11, wherein the computer system, including multiple remote replication servers and multiple database servers for at least one remote replication server and one database server, further appears as a single database server to other computer systems.

15. The remote replication system of claim 11, wherein the means for selecting one of said remote replication servers includes means for monitoring functioning status of at least each remote replication server and for routing new query requests to one of said remote replication server that is functioning.

16. The remote replication system of claim 11, wherein the computer system comprises a multi-tier computing system including multiple computers interconnected via a communication link means, at least one of said computers designated as a front end-tier computer generating said requests, and at least one of said computers designated as a back-end tier computer including said database servers, the remote replication system connected between the front-end computer and the database servers.

17. The multi-tier computing system of claim 16, wherein at least one of said multiple computers is designated as a middle-tier computer for interfacing between the front-end and back-end tier computers.

18. The multi-tier computing system of claim 16, wherein the computer system including multiple remote replication servers and multiple database servers for at least one remote replication server and one database server, further appears as a single database server to the middle tier servers.

19. The multi-tier computing system of claim 16, further includes the logical step of establishing connections using TCP/IP protocols for known IP addresses and port numbers from multiple middle tier servers to the remote replication system including multiple remote replication servers and multiple database servers for at least one remote replication server and one database server and appearing as a single database server to the middle tier servers.

20. The multi-tier computing system of claim 16, wherein said interface comprises Java Database Connectivity (JDBC), Open Database Connectivity (ODBC) or a comparable interface.

21. The multi-tier computing system of claim 16, further comprising the steps of, after processing of the new query request in said database:

receiving response from the database in relation to said new query request via the selected database sever, and communicating the response for delivery indirectly to the requester via the remote replication server or for delivery directly to the requester from the database server.

24. The computing system of claim 28, further comprises a multi-tier computing system composed of said characteristics of claims 17 through 21.

22. A computing system comprising a plurality of computers sharing a common database, said plurality of computers being interconnected via communication links, at least one of said computers being a front end computer and one or more said computers being back-end computers including multiple database servers, wherein the database servers are provided with a unified view of the data by a database remote replication system;

and said database remote replication system, comprising at least one remote replication server for receiving new query requests including database functions for operating on the data stored in said database servers, and for each new update query preserving the unified view of data among said database servers after inserting the changes of said update query request. The remote replication system further monitors the health status of all of the existing database servers and isolates any database server that is not responding from the rest of database servers. The remote replication system further synchronizes the view of data of a newly added database with the unified view of data of existing database servers prior to bringing the newly added database online wherein the synchronization procedure introduces no interruption of service in the operation of said computing system. The computing system further comprises at least one database server interface including connections for communication with said multiple database servers to send each new query requests to at least one of said multiple database servers;

wherein the remote replication system is connected between the front-end computer and the database servers.

25. A computer program product for use with a database computing system including multiple database servers for a least one database comprising:

(i) a computer readable medium;

(ii) means provided on the computer-readable medium, for establishing connections to said multiple database servers for communicating with said database servers;

(iii) means provided on the computer-readable medium, for receiving one or more query requests requiring database functions for operating on the data stored in said database servers;

(iv) means provided on the computer-readable medium, for providing the database servers with a unified view of data and for each new update query request preserving the unified view of data among said database servers after inserting the changes of said update query request;

(v) means provided on the computer-readable medium, monitoring the health status of all of the existing database servers and isolating any database server that is not responding from the rest of database servers;

(vi) means provided on the computer-readable medium, synchronizing the view of data of a newly added database with the unified view of data of existing database servers prior to bringing the newly added database online without introducing any interruption of service in the operation of said computer program product.