Section: Protection of Information Assets
Explanation:
For processing to be correct, it is essential that the proper version of a file is used. Transactions should be
applied to the most current database, while restart procedures should use earlier versions. Source
documentation should be retained for an adequate time period to enable documentation retrieval,
reconstruction or verification of data, but it does not aid in ensuring that the correct version of a file will be
used. Data file security controls prevent access by unauthorized users who could then alter the data files;
however, it does not ensure that the correct file will be used. It is necessary to ensure that all documents
have been received for processing, one-for-one; however, this does not ensure the use of the correct file.

A self-checking digit is the most effective accuracy control for entry of a valid numeric part number. This method involves adding an extra digit at the end of every number which is calculated from the other digits. This digit is then used to check the accuracy of the entered number1. While hash totals, online review of description, and comparison to historical order pattern can be used as accuracy controls, they are not as effective as a self-checking digit.

Section: Information System Acquisition, Development and Implementation