Data corruption refers to errors in computer data that occur during transmission, retrieval, or processing, introducing unintended changes to the original data. Computer storage and transmission systems use a number of measures to provide data integrity, or lack of errors. In general, when there is a data corruption, the file containing that data would be inaccessible, and the system or the related application will give an error. For example, if a Microsoft Word file is corrupted, when you try to open that file with MS Word, you will get an error message, and the file would not be opened. Some programs can give a suggestion to repair the file automatically (after the error), and some programs cannot repair it. It depends on the level of corruption, and the in-built functionality of the application to handle the error. There are various causes of the corruption.
Data corruption during transmission has a variety of causes. Interruption of data transmission causes information loss. Environmental conditions can interfere with data transmission, especially when dealing with wireless transmission methods. Heavy clouds can block satellite transmissions. Wireless networks are susceptible to interference from devices such as microwave ovens.
Data loss during storage has two broad causes: hardware and software failure. Head crashes and general wear and tear of media fall into the former category, while software failure typically occurs due to bugs in the code.
When data corruption behaves as a Poisson process, where each bit of data has an independently low probability of being changed, data corruption can generally be detected by the use of checksums, and can often be corrected by the use of error correcting codes.
If an uncorrectable data corruption is detected, procedures such as automatic retransmission or restoration from backups can be applied. Certain levels of RAID disk arrays have the ability to store and evaluate parity bits for data across a set of hard disks and can reconstruct corrupted data upon of the failure of a single or multiple disks, depending on the level of RAID implemented.
If appropriate mechanisms are employed to detect and remedy data corruption, data integrity can be maintained. This is particularly important in banking, where an undetected error can drastically affect an account balance, and in the use of encrypted or compressed data, where a small error can make an extensive dataset unusable.