Difference recording apparatus having a processing unit, recording unit, log update section, and log comparator using a classification key in a log of input data

Claim 1

A difference recording apparatus, comprising: difference detection means for detecting a log difference by using a classification key in a log of input data; processing means for restoring the log by using difference data from said difference detection means; recording means for recording the log restored by said processing means; recording limiting means for limiting recording of a log of identical data in said recording means within a unit time on the basis of the presence/absence of a difference detected by said difference detection means and an upper limit of log acquisition; and timepiece means for repeatedly counting a unit time, wherein said recording limiting means limits recording of the log of identical data within each unit time counted by said timepiece means; wherein said recording limiting means comprises a log update section for updating a log record, said log update section performing update processing for a log recording area in said recording means after the lapse of the unit time in a recording mode, wherein said processing means records difference data associated with log data which is being recorded in said recording means, when new data is input in a log recording mode, under a condition that the data have identical classification keys, and the upper limit of log acquisition has not been reached, wherein said processing means updates only a loss counter corresponding to log data of said recording means, when new data is input in the log recording mode, under one of conditions that the data have identical classification keys and no difference data is present, and that the upper limit of log acquisition has been reached, and wherein the difference is stored in the difference data and the log, which is considered identical according to the classification key, is deleted and the number of losses are counted by the loss counter, before the time passes for the renewal by the timepiece means, and wherein the difference of the input data is stored in another area and when it is considered that there is no input data difference, the data is deleted to secure a save area.