Much progress is being made in remote (control) technology typified by grid technology, wherein one computer on a computer network sends an application to run on another computer, and then commands the running of that application. Applying grid technology, for example, allows high speed processing of large scale scientific and technical calculations so as to obtain the required calculation results, and joint use of high performance computers and scientific and technical data widely dispersed on a global scale. This type of computer network is known to employ the following two methods for jointly sharing data among multiple computers.
In a first method, the computer already holding the data required for data processing (calculation) is requested to run the application. The user making the request investigates ahead of time what data is in what computer. The user then requests processing of data after sending the application to the computer that must execute the application. This method is effective when the remote computer has a sufficiently high speed processor. This method is ideal for joint data sharing methods for the scientific and technical calculation field using high performance computers.
In a second method, the data that must be processed is copied between computers. The computer making the request (or source request computer), first transfers (copies) the required data to the remote computer that will run the application and the requests that the application be run. This method is effective when the processor of the source computer making the request does not have sufficient capacity. However, this method has the problem that when attempting to remotely run an application requiring vast quantities of data, copying the data requires a significant amount of time because copying the data from the source request computer to the remote access computer is performed over a network. Therefore, the first method is generally used when an application must be run on a remote computer already holding the data.
A method is known in the technology of the related art for copying data between computers by a remote copy function contained in the disk control device. Remote copy, as referred to here, is a function wherein two disk control devices send and receive copy data by way of a dedicated channel without using a host device, and they mutually synchronize with and update (rewrite) the data stored in the respective disks. A primary disk control device and a secondary disk control device are defined for the remote copy function. When data is updated (or rewritten) on the primary disk control device, a remote copy mechanism in the primary disk control device transfers that rewritten data automatically to the secondary disk control device and that data then appears in the disk of the secondary disk control device.
Utilizing the remote copy function allows the data stored in two disk control devices at mutually separated locations to be matched (or synchronized) with each other. Therefore, when a problem occurs in the primary disk control device or in the host device (host computer) connected to the primary disk control device, the host device connected to the secondary disk control device allows the task of processing the next data to continue. Examples of use of the remote copy function in the known art are disclosed for example in JP-A No. 149499/2002 (patent document 1) and in JP-A No. 49517/2002 (patent document 2).
[Patent Document]
JP-A No. 149499/2002
[Patent Document]
JP-A No. 49517/2002
The above described data sharing methods among computers in grid technology cannot be easily applied to the database field when large amounts of data are involved. Databases are generally managed (operated) by data processing systems possessed by the customer (company). Data sharing among computers, for example, is required when the computational performance (processing ability) of one's own company system is insufficient when attempting to process vast amounts of data on a large scale database.
In this case, the data processed on the computer only exists in the database of that data processing system so that the second (data) sharing method described must be used when attempting to run a database application on another high speed computer that is connected to the network. A long time, however, is required for copying the vast amount of data stored in the database, causing the problem that database processing will stop before copying of the data is complete.
The methods described in patent documents 1 and 2 both have the objective of speeding up or simplifying system recovery after a problem has occurred. These methods do not propose data copying technology for sharing data among computers.