Importance

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Abstract

A computer system for processing and committing data comprises a processor, an external storage device such as DASD or tape coupled to the processor, and a working memory such as RAM. An application program updates data in the working memory and then requests that the data be committed, i.e. written to the external storage device. In response, an operating system function determines which data or blocks have been changed and supplies to an I/O service an identification of the changed data or blocks to cause the I/O service to write the changed data or blocks to the external storage device. Thus, the application program is not burdened with the management of the I/O. The operating system permits the program to continue with other processing while the data is being written from the working memory to the external storage device. As a result, the program need not wait while the data is written to the external storage. Also, because little time is required of the program in the commit process, the program can frequently request commits. With frequent commits, there is less chance that the data will have been written to back-up memory or back-up storage (due to an overload of the working memory) between commits, and as a result, time will not be required to read the data from the back-up memory or storage into the working memory en route to the application program's external storage. Also, the frequent commits reduce the chance of overloading the I/O subsystem.

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