A method, apparatus, and article of manufacture for a computer implemented image copying system for identifying modifications in a database in a computer. The database contains data objects and is stored on a primary data storage device connected to the computer. A data object identifier is generated...http://www.google.com.tw/patents/US6161109?utm_source=gb-gplus-share專利 US6161109 - Accumulating changes in a database management system by copying the data object to the image copy if the data object identifier of the data object is greater than the image identifier of the image copy
