Method and apparatus for reconciling different versions of a file

• US 5,600,834 A
• Filed: 04/05/1995
• Issued: 02/04/1997
• Est. Priority Date: 05/14/1993
• Status: Expired due to Term

• Current Assignee: Binary Services LLC (Intellectual Ventures LLC)
• Original Assignee: Mitsubishi Electric Information Technology Center America, Inc. (Mitsubishi Electric Corporation)
• Inventors: Howard, John H.
• Primary Examiner(s): Amsbury, Wayne
• Assistant Examiner(s): HOMERE, JEAN RAYMOND
• Application Number:
  US08/417,446
• Time in Patent Office: 671 Days
• Field of Search: 395/600, 395/200.08, 395/200.19, 364/DIG. 1
• US Class Current: 713/178
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

In a distributed file environment, a system for safely updating a file wiut risk of losing work performed at one site due to work performed on the file at another site uses a journal or log at each site which is updated after a file is modified. This log is compared with the logs from other sites before a file is used at any one site, so that new versions can be propogated automatically and safely to out-of-date sites, with the user immediately alerted if conflicting versions of the file exist at different sites. The reconciliation can be applied to collections of files, automatically updating only those files for which it is safe to and necessary do so. Since reconciliation occurs at times selected by the user, inconsistent or partially completed versions of files need not be propogated to other sites. Additionally, logs may be built incrementally by occasionally observing the state of the systems in terms of the files and their time stamps and creating additional log entries reflecting appearance, disappearance and changes of files. Furthermore, logs may be purged of obsolete entries by including additional log entries indicating the most recent time each site has participated in a reconciliation and deleting obsolete entries that all sites have seen.

Claims

1. In a computer system not utilizing a global database, but rather utilizing a collection of local databases, none of which serve as a central collection point, in which files are stored and modified at memory devices at multiple locations, apparatus for permitting the creation of new versions of a file at one location without knowledge of whether conflicting versions are created at another location, comprising:

a portable memory device transportable between locations on which a file version is stored; and

,

means for safely permitting reconciling different versions of a file transported from location to location on said portable memory device, said reconciling means including

means at first and second locations for generating a log entry at its respective location, each of said log entries including a time stamp for the version of said file on said portable memory device at said location, said timestamp serving as a unique identifier regardless of the time indicated thereby, thus to create a history of version creation and modification for said file at said first and second locations;

means at said first location for entering said log entry into said portable memory device;

means at said second location for reading out the log entry on said portable memory device and for combining the log entry from said portable memory device and a log entry at said second location so as to compare both modified versions and respective timestamps to indentify missing entries or confliction updates represented by different timestamps and thus the existence of different versions of said file;

means at said second location and upon said identification of different versions of said file for determining actions necessary to synchronize said different versions; and

,

means at said second location for determining if such synchronizing action would result in loss of information, whereby combination of all versions of said file may be safely accomplished at said second location.

2. The apparatus of claim 1, and further including means for performing the determined synchronizing actions by copying or deleting files.

3. The apparatus of claim 2, and further including means for notifying the user if said synchronizing actions would result in loss of information.

4. The apparatus of claim 1, and further including means for purging obsolete log entries by purging a first entry if there exists a subsequent entry for the same file and if that subsequent entry is available at all other locations.