Update log management device and an update log management method decreasing the data amount of transmitting and the update log amount of holding based on the result of comparing the amount of the update log with the amount of the updated data plus the log applied information

Claim 2

An update log management device used in a data sharing system for maintaining and storing a data replicated among a plurality of devices connected in a network, comprising: a storage for recording a plurality of update logs wherein each one of the plurality of update logs shows an update of the data; an extracting unit for extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; a comparing unit for calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of log applied information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; a transmitting unit for transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y); and a deleting unit for deleting the at least one of update logs from the storage if X>Y is true for all of the devices.

Claim 3

The update log management device according to claim 1 , wherein the storage records a log record information which is an information indicating which update logs are stored by each one of the plurality of devices, wherein the extracting unit decides the at least one of update logs to transmit to the another device based on the log record information.

Claim 4

The update log management device according to claim 2 further comprising an excluding unit for selectively deleting the log record information of an unused device from the storage.

Claim 5

The update log management device according to claim 3 , wherein the excluding unit sets a time limit beforehand and deletes the log record information from the storage that is not updated during the time limit.

Claim 6

The update log management device according to claim 3 , wherein the update log management device sets an identifier which specifies a plurality of devices for sharing the data as one domain, and hold the log record information of the plurality of devices identified by the identifier and does not hold the log record information of the other devices.

Claim 7

The update log management device according to claim 3 , wherein the excluding unit receives a signal from the unused device for requesting deletion of the log record information of the unused device, and deletes the log record information of the unused device.

Claim 8

The update log management device according to claim 3 , wherein the excluding unit deletes the log record information of a second device stored at a first device when X>Y is true for all the data stored in the first device.

Claim 9

An update log management device used in a data sharing system for maintaining and storing an identical data between a plurality of devices connected in a network, comprising steps of: recording a plurality of update logs, wherein each one of the plurality of update logs shows an update of the data; extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of log applied information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y); and deleting the at least one of update logs from the storage if X>Y is true for all of the devices.

Claim 10

An update log management device used in a data sharing system for maintaining and storing an identical data between a plurality of devices connected in a network, comprising steps of: recording a plurality of update logs, wherein each one of the plurality of update logs shows an update of the data; extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of log applied information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y); and deleting the at least one of update logs from the storage if X>Y is true for all of the devices.

Claim 11

An update log management device used in a data sharing system for maintaining and storing a data replicated among a plurality of devices connected in a network, comprising: a storage for recording a plurality of update logs wherein each one of the plurality of update logs shows an update of the data; an extracting unit for extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; a comparing unit for calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of an information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; a transmitting unit for transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y) ; and a deleting unit for deleting the at least one of update logs from the storage if the deleting unit decides that the at least one of update logs are not required to be transmitted to any of the other devices, or if X>Y is true for all of the other devices that have not yet received the extracted at least one of update logs.

Claim 12

An update log management device used in a data sharing system for maintaining and storing a data replicated among a plurality of devices connected in a network, comprising: a storage for recording a plurality of update logs wherein each one of the plurality of update logs shows an update of the data; an extracting unit for extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; a comparing unit for calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of an information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; a transmitting unit for transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y) ; and a deleting unit for deleting the at least one of update logs from the storage if the deleting unit decides that the at least one of update logs are not required to be transmitted to any of the other devices, or if X>Y is true for all of the other devices that have not yet received the extracted at least one of update logs.

Claim 13

An update log management device used in a data sharing system for maintaining and storing an identical data between a plurality of devices connected in a network, comprising steps of: recording a plurality of update logs, wherein each one of the plurality of update logs shows an update of the data; extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of an information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y) ; and deleting the at least one of update logs from the storage if the deleting unit decides that the at least one of update logs are not required to be transmitted to any of the other devices, or if X>Y is true for all of the other devices that have not yet received the extracted at least one of update logs.

Claim 14

An update log management device used in a data sharing system for maintaining and storing an identical data between a plurality of devices connected in a network, comprising steps of: recording a plurality of update logs, wherein each one of the plurality of update logs shows an update of the data; extracting at least one of update logs from the plurality of update logs stored in the storage to transmit to another device to maintain the identical data among the plurality of devices; calculating data amount X which is an addition of data amount of the at least one of update logs for transmitting to the another device extracted by the extracting unit, and for calculating data amount Y which is an addition of data amount of the data itself plus data amount of an information indicating that the at least one of update logs is already applied to the data itself, and for comparing the data amount X and the data amount Y; transmitting the data itself and the information indicating that the at least one of update logs is already applied to the data to the another device if the data amount X of the at least one of update logs exceeds the data amount Y (X>Y), and for transmitting the at least one of update logs to the another device if the data amount X of the at least one of update logs does not exceed the data amount Y (X≦Y) ; and deleting the at least one of update logs from the storage if the deleting unit decides that the at least one of update logs are not required to be transmitted to any of the other devices, or if X>Y is true for all of the other devices that have not yet received the extracted at least one of update logs.