Patent ID: 6684226
Filing Date: 2004-01-27
Classification: G06F,Y10S

Abstract:
A method for storing information stored in one or more files on a permanent storage medium, comprising the steps of:storing data transaction-wise according to a shadow paging principle, retaining, in a commit operation, the previous data and their physical storage on the storage medium together with a separate storage on the storage medium representing new data as changes to the previous data, the previous data and the changes together constituting, upon commit, a new version of the data, both the previous and the new versions of the data being separately accessible, wherein the data are stored as a number of individually addressable data blocks, addresses representing the physical storage of the individual data blocks being stored in a tree structure of one or more first data elements, and wherein the storing step comprises: identifying data blocks to be modified, copying the identified data blocks, performing the modification(s) on the copied data blocks, storing the modified data blocks at addresses not coinciding with any of the addressable data blocks or any of the first data elements, for each identified data block, identifying one or more of the first data elements of the tree structure from a root of the tree structure to the data block, copying each identified data element at an address not coinciding with any of the addressable data blocks or any of the first data elements, replacing, in each copied first data element, the address of the identified data block or first data element with the address of the corresponding modified data block or first data element, and providing a new root of the modified tree structure and having the new root represent the modified first data element corresponding to the first data element represented by the root of the tree structure.