Showing papers on "Data Corruption published in 1998"

Method and apparatus for detecting and recovering from data corruption of a database via read prechecking and deferred maintenance of codewords

Abstract: A method of detecting and recovering from data corruption of a database is characterized by the step of protecting data of the database with codewords, one codeword for each region of the database; and verifying that a codeword matches associated data before the data is read from the database to prevent transaction-carried corruption. A deferred maintenance scheme is recommended for the codewords protecting the database such that the method of detecting and recovering from data corruption of a database may comprise the steps of protecting data of the database with codewords, one codeword for each region of the database; and asynchronously maintaining the codewords to improve concurrency of the database. Moreover, the database may be audited by using the codewords and noting them in a table and protecting regions of the database with latches. Once codeword values are computed and checked against noted values in memory, a flush can cause codewords from outstanding log records to be applied to the stored codeword table.

Data corruption detection apparatus and method

Abstract: A system and method for providing detection of the signatures effected by a defective Floppy Diskette Controller (“FDC”) operates on media independent of files thereon, or on files, independent of the media on which they are stored. Multiple testing strategies incorporate evaluations to detect signatures of data corruption introduced by defective FDCs from long transfer delays, short transfer delays, contiguous storage of logical sectors, or fragmented storage of logical sectors of a file. A false positive filter uses secondary testing of data. Filters remove from consideration those common patterns that properly and naturally occur. These filters rely on indicia demonstrating that primary leading indicators of the presence of an error do not really result from an actual error. The signatures may be detected regardless of subsequent transfer of corrupted files to various media including the media tested.

Failsafe asynchronous data transfer corruption indicator

Abstract: A data corruption indicator circuit for providing error free data transfer between a first device and a second device, clocked by different clock signals, is implemented. The data corruption indicator circuit can allow for faster throughput than the described prior art and provides a circuitry for detecting corrupt data. The data corruption indicator circuit provides a clocked data ready signal that updates a status lip-flop and a delayed data ready signal that updates a plurality of data flip-flops and a potential corruption flip-flop. Additionally, the delayed data ready signal may be used as an interrupt signal to notify the second device that data is available for transfer. The delay between the clocked data ready signal and the delayed data ready signal is such that a hazard cannot exist for the data signal and the status signal simultaneously. The failsafe nature of the invention is that while the status signal may indicate corrupt data when the data is actually valid, it will not indicate valid data when the data is corrupt.

Method and apparatus for controlling image data transfer in a photographic film scanner

Abstract: A photographic film scanner has a line integration light sensor and a programmed controller which employs a plurality of lookup tables (LUT) sequenced by a common timer to control the timing of data collection and transfer to an asynchronously operating host computer. Delays in the transfer of image data to the host computer which exceed the light sensor line integration time can cause the integrated pixel scan information to become corrupted. Data corruption caused by delays in excess of line integration time is avoided by disabling the light sources and the related image scan operations until it is determined that prior line data transfer to the host is completed whereupon the accumulated data is collected and transferred to the host computer and normal scan operations are re-initiated. Even with the LEDs disabled, excessive build-up of dark current in the light sensors can corrupt the accumulated image information in the light sensor. This corruption is prevented by detecting the excessively long delay, flushing the corrupted data out of the light sensor and re-scanning the image line to develop a fresh line of image data for transfer to the host computer.

Shrinkage Figures and Data Corruption: Lies, Damned Lies and Statistics?

Abstract: Effective security requires accurate data about losses. In retailing, estimates of loss known as ‘shrinkage’ are commonly used to indicate problems within a store. However, shrinkage not only includes theft by staff and customers but also some degree of unidentified ‘clerical’ error. Understanding how data is created and corrupted, is a vital part of understanding estimates of risk. By reducing data corruption, more reliable loss figures are produced on which to base security decisions. This is a vital component of any security strategy designed to increase the risk for offenders. This paper presents results from a twelve-month study of data corruption within a medium-sized jeans and casual clothing retailer. Using both hypothetical examples and case studies of real stock figures, the paper demonstrates how data is corrupted and how corruption impacts on stocktakes, loss figures, merchandising and sales.