Distributed synchronization of databases

Abstract

A computer implemented method is provided for synchronizing a first database located on a first computer and a second database located on a second computer. At the first computer, it is determined whether a record of the first database has been changed or added since a previous synchronization, using a first history file located on the first computer comprising records representative of records of the first database at the completion of the previous synchronization. If the record of the first database has not been changed or added since the previous synchronization, the first computer sends the second computer information which the second computer uses to identify the record of the first database to be unchanged.

What is claimed is:  
     
         1 . A computer implemented method for synchronizing a first database located on a first computer and a second database located on a second computer, the method comprising: 
 determining, at the first computer, whether a record of the first database has been changed or added since a previous synchronization, using a first history file located on the first computer comprising records representative of records of the first database at the completion of the previous synchronization;    if the record of the first database has not been changed or added since the previous synchronization, sending from the first computer to the second computer information which the second computer uses to identify the record of the first database to be unchanged.    
     
     
         2 . The computer implemented method of  claim 1  wherein a second history file located on the second computer contains records representative of records of the first database at the completion of the previous synchronization, wherein one of the representative records represents the record of the first database determined to be unchanged, and the method further comprises performing a synchronization, at the second computer, of the second and first databases using the one of the representative records.  
     
     
         3 . The computer implemented method of  claim 2  wherein the information sent from the first computer to the second computer is used to locate the one of the representative records in the second history file.  
     
     
         4 . The computer implemented method of  claim 3  wherein the second history file stores information in relation to the representative records and wherein the one of the representative records in the second history file can be identified from the stored information.  
     
     
         5 . The computer implemented method of  claim 4  wherein the information sent from the first computer to the second computer comprises information that matches the information stored in relation to the one of the representative records in the second history files.  
     
     
         6 . The computer implemented method of  claim 1  wherein the information comprises information identifying records other than the unchanged record.  
     
     
         7 . The computer implemented method of  claim 1  wherein the information comprises information identifying the unchanged record.  
     
     
         8 . The computer implemented method of  claim 1  wherein the information comprises information identifying the deleted records.  
     
     
         9 . The computer implemented method of  claim 1  wherein the information comprise information identifying the added records.  
     
     
         10 . The computer implemented method of  claim 1  wherein the information comprises a code, the code being based on at least a portion of the content of the record of the first database.  
     
     
         11 . The computer implemented method of  claim 10  wherein the code comprises a hash number computed based on at least a portion of the content of the record of the first database.  
     
     
         12 . The computer implemented method of  claim 10  wherein the information further comprises a first plurality of records of the first database identified as “changed or added”, the method further comprises using said information to indentify a plurality of the first database as “deleted or changed” since the previous synchronization.  
     
     
         13 . The computer implemented method of  claim 1  wherein the information comprises a code uniquely identifying the records of the first database.  
     
     
         14 . The computer implemented method of  claim 13  wherein the unique identification code is assigned by the first database to the records of the first database.  
     
     
         15 . The computer implemented method of  claim 14  wherein the information further comprising a first plurality of the records of the first database identified as “changed”, a second plurality of the records of the first database identified as added, and information identifying a third plurality of records of the first database as “deleted”.  
     
     
         16 . A computer implemented method of identifying a record of a database stored on a first computer to a second computer comprising: 
 reading a record of the database;    assigning a code to the record of the database, the code being based on at least a portion of the content of the record of the first database;    transmitting the code to the second computer to identify the record to the second computer.    
     
     
         17 . The computer implemented method of  claim 16  wherein the code comprises a hash number computed based on at least a portion of the content of the record of the first database.  
     
     
         18 . A computer program, resident on a computer readable medium for synchronizing a first database located on a first computer and a second database located on a second computer, comprising instructions for: 
 determining, at the first computer, whether a record of the first database has been changed or added since a previous synchronization, using a first history file located on the first computer comprising records representative of records of the first database at the completion of the previous synchronization;    if the record of the first database has not been changed or added since the previous synchronization, sending from the first computer to the second computer Information which the second computer uses to identify the record of the first database to be unchanged.    
     
     
         19 . The computer program of  claim 18  wherein a second history file located on the second computer contains records representative of records of the first database at the completion of the previous synchronization, wherein one of the representative records represents the record of the first database determined to be unchanged, and the program further comprising instructions for performing a synchronization, at the second computer, of the second and first databases using the one of the representative records.  
     
     
         20 . The computer program of  claim 19  wherein the information sent from the first computer to the second computer is used to locate the one of the representative records in the second history file.  
     
     
         21 . The computer program of  claim 20  wherein the second history file stores information in relation to the representative records and wherein the one of the representative records in the second history file can be identified from the stored information.  
     
     
         22 . The computer program of  claim 21  wherein the information sent from the first computer to the second computer comprises information that matches the information stored in relation to the one of the representative records in the second history files.  
     
     
         23 . The computer program of  claim 18  wherein the information comprises information identifying records other than the unchanged record.  
     
     
         24 . The computer program of  claim 18  wherein the information comprises information identifying the unchanged records.  
     
     
         25 . The computer program of  claim 18  wherein the information comprises information identifying the deleted records.  
     
     
         26 . The computer program of  claim 18  wherein the information comprise information identifying the added records.  
     
     
         27 . The computer program of  claim 18  wherein the information comprises a code, the code being based on at least a portion of the content of the record of the first database.  
     
     
         28 . The computer program of  claim 27  wherein the code comprises a hash number computed based on at least a portion of the content of the record of the first database.  
     
     
         29 . The computer program of  claim 27  wherein the information further comprises a first plurality of records of the first database identified as “changed or added”, the program further comprising instructions for using said information to indentify a plurality of the first database as “deleted or changed” since a previous synchronization.  
     
     
         30 . The computer program of  claim 18  wherein the information comprises a code uniquely identifying the record of the first database.  
     
     
         31 . The computer program of  claim 30  wherein the unique identification code is assigned by the first database to the record of the first database.  
     
     
         32 . The computer program of  claim 30  wherein the information further comprises a first plurality of the records of the first database identified as “changed”, a second plurality of the records of the first database identified as added, and information identifying a third plurality of records of the first database as “deleted”.  
     
     
         33 . A computer program, resident on a computer readable medium, for identifying a record of a database stored on a first computer to a second computer comprising instructions for: 
 reading a record of the database;    assigning a code to the record of the database, the code being based on at least a portion of the content of the record of the first database;    transmitting the code to the second computer to identify the record to the second computer.    
     
     
         34 . The computer program of  claim 33  wherein the code comprises a hash number computed based on at least a portion of the content of the record of the first database.