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System for maintaining data coherency in cache memory by periodically broadcasting a single invalidation report from server to clients

  • US 5,706,435 A
  • Filed: 07/26/1996
  • Issued: 01/06/1998
  • Est. Priority Date: 12/06/1993
  • Status: Expired due to Term
First Claim
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1. A method for maintaining coherency between a server processor that stores a plurality of data values and a plurality of client processors across a communications network, each of the client processors having a cache memory for storing a respective subset of the plurality of data values, comprising the steps of:

  • (a) broadcasting a single invalidation report from the server processor across the communications network to each of the plurality of client processors, periodically, each periodic invalidation report including information identifying any of the plurality of data values that have been updated within a predetermined period of time before the server processor broadcasts the invalidation report;

    (b) determining, based on the single invalidation report, whether a selected data value in the cache memory of each respective client processor has been updated in the server processor since the selected data value was stored in the respective cache memory, the determining performed by each respective client processor based on a respective copy of the single invalidation report received by that client processor; and

    (c) Invalidating the selected data value in the cache memory of each respective one of the plurality of client processors having the selected data value stored in the cache thereof, if the client processors determine that the selected data value has been updated in the server processor, thereby maintaining coherency without requiring information in the server identifying in which of the plurality of client processors each of the plurality of data values are stored.

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