Error detection/correction and fault detection/recovery – Data processing system error or fault handling – Reliability and availability
Reexamination Certificate
1999-02-01
2001-08-28
Shin, Christopher B. (Department: 2182)
Error detection/correction and fault detection/recovery
Data processing system error or fault handling
Reliability and availability
C707S793000
Reexamination Certificate
active
06282672
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method, apparatus and computer program for taking a backup copy of the contents of an external storage device to be accessed by a data processing system. More particularly, the present invention relates to a method, apparatus and computer program for simultaneously executing any one of a plurality of applications (computer programs) that must be executed using static data not modified by another computer program after a particular point in time and another application which must be executed using updated data.
BACKGROUND OF THE INVENTION
Accompanying the recent increase in the use of data processing systems, and the extension of business hours or the shift to 24-hour uninterrupted operation, it has become difficult to allocate time, after stopping execution of an application for updating data, for execution of an application for processing data in a static state in which no data updating operation is being performed. It should be noted that an application can, for example, be a computer program or any other such means for performing a particular processing on data. The application for processing data could, for example, be a computer program for taking a backup copy, executing statistical processing on daily business results, etc. Hence, apparatus have been sought for simultaneously executing an application for performing a data updating operation and an application that must be executed in the state in which no data updating operation has been performed.
To solve the above Japanese Patent Laid-open No. Hei 5-94265 proposes a mechanism in which, in a multiple-writing filing system, the multiple-writing configuration is cleared and an application is allowed to update one of the cleared devices. The controller takes a backup copy of the other device in a static state in which no updating operation is being performed.
Japanese Patent Laid-open No. Hei 6-44010 proposes that all or part of a data set to be affected by an updating operation is written to a subsystem memory. The update is then written to the subsystem memory to complete the updating operation. In response to an input request from the backup copy, the data in the not-updated portion is input from the original data set, and the data in the updated portion is input from the subsystem memory.
The method disclosed in Japanese Patent Laid-open No. Hei 5-94265 does not consider a situation in which an application other than an application taking a backup copy references static data that has not been updated. Therefore, this conventional arrangement must execute an application that requires static data after storing a backup copy taken by the backup copy taking application into an external storage device to maintain the logical integrity of the data.
The method disclosed in Japanese Patent Laid-open No. Hei 6-44010 does not consider application of the disclosed technology to any type of application. Therefore, this conventional arrangement needs to be aware of whether an area for data input/output operations by each application requiring application of the disclosed technology has been updated or not. This presents problems of making applications complicated and pushes up the cost of the entire system.
SUMMARY OF THE INVENTION
The present invention provides improvements in a method, apparatus and a computer program for applying, to any given application, a capability of inputting/outputting static data not modified by any application after a particular point in time without affecting an application requiring a data updating operation in an external storage device associated with an access operation by a data processing system.
According to one aspect of the invention, a duplicate of data stored in an external storage device requiring input/output of static data not modified by an application after a particular point in time is taken. A static data input/output controller for controlling a data input/output request to the external storage device and the duplicate thereof and a static data input/output identification data defining module for identifying whether a data input/output request is for static data are arranged in a processing unit. The static data input/output controller determines whether the source of the data input/output request requests static data based on the information in the static data input/output identification information defining module. If the input/output request is for the static data not modified by an application after a particular point in time, the static data input/output controller performs a data input/output operation on one external storage device with the static data. For other input/output requests, the controller performs a data input/output operation on the other external storage device.
Some applications complete logical input/output processing of data upon completion of two or more data input/output requests. To allow these applications to reference the static data having logical integrity these applications are cooperatively associated. Access by these applications to the external storage device is temporarily discontinued in a state in which the logical integrity of the data is maintained, and then the static data input/output controller is started.
Other applications complete logical input/output processing of data upon completion of the data input/output requests of two or more external storage devices. To allow these applications to reference the static data having logical integrity, the start processing of the static data input/output controller for these two or more external storage devices is performed all at once, thereby allowing reference to the static data in these two or more external storage devices at a same point in time having the data logical integrity.
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Bandoh Toshiyuki
Ishikawa Satoshi
Miyata Katsuhisa
Shinmura Yoshiaki
Torii Masakazu
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Shin Christopher B.
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