Database management system and method for controlling synchronization between databases

A database management system comprising:

• databases for a synchronization source and a synchronization destination;
• a management server for controlling data synchronization between databases of the synchronization source and the synchronization destination;
• a table for storing entries at least including an identifier for identifying a record of the database of the synchronization source, and a synchronization flag indicating whether the record is non-synchronized or synchronized between the databases of the synchronization source and the synchronization destination;
• wherein the management server
• executes switching from a synchronization control based on a table method, which performs data synchronization between databases by transmitting the record where the synchronization flag extracted from the table is set to non-synchronized from the database of the synchronization source to the database of the synchronization destination, to a synchronization control based on a query transmission method, which utilizes an update log to perform data synchronization between databases by transmitting an update log extracted from the database of the synchronization source to the database of the synchronization destination;
• and
• based on a non-synchronized status and a synchronized status indicated by the synchronization flag in the table, periodically calculates a remaining synchronization time when synchronization is continued based on the table method and a remaining synchronization time by switching to the query transmission method, and when it is determined that the remaining synchronization time by switching to the query transmission method is shorter based on the result of the calculation, sets a timing for executing the switching.