A method for producing a duplication of a database stored in an external storage by writing over copy data of the database with update log data which was acquired after acquisition of the copy data. This method is implemented in a computer system having a virtual storage operating system. The system...http://www.google.co.uk/patents/US5321832?utm_source=gb-gplus-sharePatent US5321832 - System of database copy operations using a virtual page control table to map log data into physical store order
