Method of synchronizing data between databases, and computer system and computer program for the same

A computing device program product for synchronizing data in response to a retrieval request between a first database and at least one second database each holding at least a portion of data included in the first database using a computing device, the computing device program product comprising:

• a computer readable medium;
• first programmatic instructions for extracting from the first database, in response to issuing the a retrieval request to the second database, differential data corresponding with the retrieval request between a first data set in the first database and a second data set in the second database as a retrieval target of the retrieval request, wherein the retrieval request includes a current retrieval request and a future retrieval request, wherein the future retrieval request is configured for issuance after the current retrieval request;
• and
• second programmatic instructions for updating the second data set by applying only the differential data corresponding with the retrieval request to the second database and by recording a time of updating the second data set, wherein the updated second data set is the retrieval target of the retrieval request, wherein the differential data corresponding with the retrieval request represents only a portion of data out of all possible data sets that differ between the first database and the second database, and wherein the differential data indicates a difference between the second data set at a time of issue of a past retrieval request wherein the time of issue of the past retrieval issued before the retrieval request, and the second data set at the time of issue of the retrieval request.

A computer system for synchronizing data in response to a retrieval request between a first database and one or more second databases, each holding at least one piece of data included in the first database, the computer system comprising:

• a processor;
• a differential data extracting section for extracting, from the first database in response to issuing a the retrieval request to the second database, differential data corresponding with the retrieval request between a first data set in the first database and a second data set in the second database as a retrieval target of the retrieval request, wherein the retrieval request includes a current retrieval request and a future retrieval request, wherein the future retrieval request is configured for issuance after the current retrieval request;
• and
• an update section for updating the second data set by applying only the differential data corresponding with the retrieval request to the second database and by recording a time of updating the second data set, wherein the updated second data set is the retrieval target of the retrieval request, wherein the differential data corresponding with the retrieval request represents only a portion of data out of all possible data sets that differ between the first database and the second database, and wherein the differential data indicates a difference between the second data set at a time of issue of a past retrieval request wherein the time of issue of the past retrieval issued before the retrieval request, and the second data set at the time of issue of the retrieval request.