Data processing method for file status recovery includes providing a log

Abstract

A data processing system includes both volatile and nonvolatile memories, user-inaccessible file control software and performs a method for recovering from a malfunction occurring during a file transaction that prevents accomplished microscopic transactions from being lost. The method comprises the steps of: providing a log file to maintain a record of file transactions which may span both the volatile and nonvolatile memories; recording in the portion of the log file in volatile memory, old and new data images which result during a file transaction; writing the old and new data images to a portion of the log file which is contained in nonvolatile memory, with the new data image being written after it is certain that the old data image is present in the nonvolatile memory; and in the event of a malfunction, employing the log file in nonvolatile memory to determine the status of a file transaction and rolling back the transaction in the event the malfunction occurred prior to its completion, and further assuring that all file system actions have actually occurred for transactions marked as completed.