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Replica administration without data loss in a store and forward replication enterprise

  • US 5,787,247 A
  • Filed: 07/12/1996
  • Issued: 07/28/1998
  • Est. Priority Date: 07/12/1996
  • Status: Expired due to Term
First Claim
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1. In a computer network where copies of data objects are replicated among a plurality of replica nodes that are logically connected to provide a data flow path from each replica node to any other replica node in the network, and each replica node being capable of making changes to the replicated data objects and each being capable of storing the changes made either locally or by any other node, and each being capable of providing access to such stored changes by any other replica node in the network, a method of removing a local copy of a data object from a local replica node in the computer network while protecting against inadvertent loss of any changes made to the local data object prior to its removal at the local replica node, the method comprising the steps of:

  • saving, at a local replica node, changes made to a local copy of a data object by the local replica node and changes made by and received from other replica nodes on a computer network so that the local copy of the data object reflects all such changes made to the data object;

    transmitting to at least one other replica node in the network any changes which have been made to the local copy of the data object by the local replica node and which have not previously been transmitted to at least one other replica node in the network in order to preserve said changes and ensure continued availability of said changes by virtue of their storage in said at least one other replica node of the network;

    verifying that the saved changes reside on at least one other replica node in the network prior to removal of the local copy of the data object from the local replica node by (1) sending a message to said at least one other replica node, and by (2) positively confirming that the saved changes reside on the at least one other replica node if the combination of all changes on all replica nodes other than the local replica node include at least the saved changes;

    removing the local copy of the data object from the local replica node if said saved changes reside on at least one other replica node without removing any changes from said at least once other replica node; and

    accessing said saved changes from at least one replica node in the network.

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