To enable data updating on a present site or ordinary processing which is not related to data updating, although such processing is disabled conventionally when data updating is disabled by a fault on an opposite site.

A mobile agent 8 is used for a data copy function 11 and when a database 2 is updated on a site A, updating transaction data are generated from updating contents by detecting such updating. Then, a database 2A is updated by executing an updating transaction by moving to a site B. Even when any fault occurs on the site B or network 7, the mobile agent is waited until recovery from the fault and when the fault is recovered, updating processing is performed. On the other hand, even when such a fault occurs, a computer 5 of the site A can perform data updating processing to the database 2 since it is completely separated from processing in the mobile agent, and processing except for updating processing can be performed as well.