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Parallel, distributed optimistic concurrency control certification using hardware filtering

  • US 5,263,156 A
  • Filed: 12/20/1990
  • Issued: 11/16/1993
  • Est. Priority Date: 12/20/1990
  • Status: Expired due to Term
First Claim
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1. In a database transaction certification system for a database transaction processing system, said certification system having a memory, a plurality of filters connected to said memory by a communications channel, each of said filters having a filter controller, and processor means connected to said memory and connected to said filter controllers, a method for determining in parallel possible multiple conflicts, each conflict being between a specific transaction and one or more other transactions whose execution overlaps the execution of said specific transaction, said method comprising the steps ofstoring in said memory a log comprising the read-sets and write-sets of said other transactions, said log comprising history, accepted, and pending relations, where said history relation contains read-sets and write-sets that have been previously applied to the database due to previously completed transactions, where said accepted relation contains read-sets and write-sets that have not been applied to the database but are due to previously certified transactions, and where said pending relation contains read-sets and write-sets that have not been applied to the database and are due to transactions awaiting certification,writing from said processor means into said log in said memory a read-set and a write-set of said specific transaction,transmitting from said processor means to one of said filter controllers selection criteria for the one filter associated with said one filter controller identifying the read-set and write-set of said specific transaction,broadcasting over said communications channel said log comprising data items which include the read-sets and write-sets of said other transactions and the read-set and write-set of said specific transaction,utilizing said one filter to identify in said broadcast log data items meeting said selection criteria identifying said read-set and write-set of said specific transaction, anddetermining if a conflict exists by determining if said one filter identifies data items from said broadcast log in addition to the read-set and write-set of said specific transaction.

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