The KIPS Transactions:PartD (정보처리학회논문지D)

Korea Information Processing Society (한국정보처리학회)
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Optimistic Concurrency Control based on 2-Version and TimeStamp for Broadcast Environment : OCC/2VTS

방송환경에서 이중 버전과 타임스탬프에 기반을 둔 낙관적 동시성 제어 기법

  • Lee, Uk-Hyun (Dept.of Computer Science, Graduate School of Chonnam National Universityisy) ;
  • Hwang, Bu-Hyun (Dept.of Computer Science, Chonnam National University)
  • 이욱현 (전남대학교 대학원 전산학과) ;
  • 황부현 (전남대학교 전산학과, 전남대학교 정보통신연구소)
  • Published : 2001.04.01
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Abstract

The broadcast environment is asymmetric communication aspect that is typically much greater communication capacity available from server to clients than in the opposite direction. In addition, most of mobile computing systems only allow the generation of read-only transactions from mobile clients for retrieving different types of information such as stock data, traffic information and news updates. Since previous concurrency control protocols, however, do not consider such a particular characteristics, the performance degradation occurs when those schemes are applied to the broadcast environment having quite a high data contention. In this paper, we propose OCC/2VTS (Optimistic Concurrency Control based on 2-Version and TimeStamp) that is most appropriate for broadcast environment. OCC/2VTS lets each client process and commit query transactions for itself by using two version data in cache. If the values of appropriate data items are not changed twice by invalidation report after a query transaction starts, the query transaction is committed safely independent of commitment of update transactions. OCC/2VTS decreases the number of informing server for the purpose of commitment. Due to broadcasting the validation reports including updated recent values, it reduces the opportunity of requesting a recent data values of server as well. As a result, OCC/2VTS makes full use of the asymmetric bandwidth. It also improves transaction throughput by increasing the query transaction commit ratio as much as possible.

방송환경은 서버(server)와 클라이언트간 대역폭이 서버에서 클라이언트쪽으로는 크고 클라이언트에서 서버쪽으로의 대역폭은 상대적으로 많이 작은 비대칭적(asymmetric) 특수한 환경이다. 또한 대부분의 방송 환경 응용시스템들은 클라이언트측에서 발생한 주로 주식 데이터, 교통 정보와 새로운 뉴스와 같은 여러 가지 다양한 정보를 검색하는 읽기전용 즉 질의 거래들을 허락한다. 그러나, 기존의 여러 가지 동시성 제어 기법들은 이러한 특수성을 고려하지 않음으로써 꽤 높은 데이터 경쟁 상태의 방송 환경에 적용될 때 성능 감소가 일어난다. 이 논문에서는 방송환경에서 가장 적절한 OCC/2VTS(Optimistic Concurrency Control based on 2-Version and TimeStamp)를 제안한다. OCC/2VTS는 캐쉬 내에 두 버전을 사용함으로써 타임스탬프 기법으로 클라이언트가 질의 거래를 자체 해결 할 수 있도록 하였다. 질의 거래 시작 후 2번의 무효화 방송을 통해 읽기 연산 대상 데이터 항목의 값이 바뀌지 않는다면 질의 거래가 갱신 거래의 완료와 상관없이 무사히 완료된다. 그 결과 첫째, 서버에게 완료 요구를 위해 정보를 보내는 기회가 감소하고 무효화 보고서 내에 갱신된 최신의 값을 포함하여 클라이언트들에게 방송함으로써 최근 데이터 값을 서버에게 요구하는 기회를 줄여 비대칭적 대역폭을 효율적으로 활용한다. 둘째, 질의 거래의 완료율을 최대한 높여 처리율을 향상시킨다.

Keywords

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