• Title/Summary/Keyword: 무효화 메시지

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Asynchronous Cache Invalidation Strategy to Support Read-Only Transaction in Mobile Environments (이동 컴퓨팅 환경에서 읽기-전용 트랜잭션을 지원하기 위한 비동기적 캐쉬 무효화 기법)

  • Kim, Il-Do;Nam, Sung-Hun
    • The KIPS Transactions:PartC
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    • v.10C no.3
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    • pp.325-334
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    • 2003
  • In stateless server, if an asynchronous cache invalidation scheme attempts to support local processing of read-only transaction in mobile client/sever database systems, a critical problem may occur ; the asynchronous invalidation reports provide no guarantees of waiting time for mobile transactions requesting commit. To solve this problem, the server in our algorithm broadcasts two kind of messages, asynchronous invalidation report to reduce transaction latency and periodic guide message to avoid the uncertainty of waiting time for the next invalidation report. The asynchronous invalidation report has its own sequence number and the periodic guide message has the sequence number of the most recently broadcast asynchronous invalidation report. A mobile client checks its cache validity by using the sequence numbers of these messages.

A Concurrency Control Method using Data Group Information in Mobile Computing Environments (이동 컴퓨팅 환경에서 데이타 그룰 정보를 이용한 동시성 제어 방법)

  • Kim, Dae-In;Hwang, Bu-Hyun
    • Journal of KIISE:Databases
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    • v.32 no.3
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    • pp.315-325
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    • 2005
  • In mobile computing environments, a mobile host caches the data items to use the bandwidth efficiently and improve the response time of transactions. If the data items cached in mobile host are updated in the server, the server broadcasts an invalidation report for maintaining the cache consistency of mobile hosts. However, this method has a problem that the response time of mobile transactions can be long since their commit decision is delayed until receiving the invalidation report from the server In this paper, we propose the USR-MT method for improving the response time of mobile transactions. As the UGR-MT method can make a commit decision by using the data group information before receiving the invalidation report, the response time of mobile transactions can be improved. Also our method can improve the cache's efficiency since it prevents all the contents of a cache from being invalidated in the case that the disconnection of a mobile host is longer than the broadcast period of invalidation report.

Adaptive Cache Maintenance Scheme based on Connection States in Mobile Computing Environments (이동 컴퓨팅 환경하의 연결 상태를 기반으로 한 적응적 캐쉬 유지 기법)

  • Nam, Sung-Hun;Cho, Sung-Ho;Hwang, Chong-Sun
    • Journal of KIISE:Information Networking
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    • v.27 no.2
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    • pp.149-159
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    • 2000
  • In mobile computing environments, invalidation and propagation method based on broadcasting is used to transmit the information for cache maintenance of mobile hosts. Previous researches generally adopted invalidation method that easily adapts to the limited network bandwidth and the frequent disconnection. But the invalidation of frequently accessed data causes the contention on the wireless network with the increasing cache requests. Although the propagation method can reduce the cache requests, the high probability of broken message or loss of message is the main factor that degrades the system performance. To resolve these problems, we propose adaptive cache maintenance scheme that dynamically adjusts the broadcasting ratio of invalidation and propagation, according to the wireless network connection states. The proposed scheme broadcasts the propagation message in stable connection state, so it can reduce the cache requests and server response time. With the decreasing available network bandwidth by the frequent partial disconnection and disconnection, the proposed scheme dynamically increases the broadcasting ratio of the invalidation messages to minimize the broken message or the loss of message probability. Consequently, the proposed scheme resolves the problems which arise in the invalidation or propagation method in mobile computing environments.

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A Strategy to maintain Cache Consistency in Mobile Computing Environments using the Asynchronous Broadcasting (비동기적 방송을 사용하는 이동 컴퓨팅 환경에서 캐쉬 일관성 유지 정책)

  • Kim, Dae-Ong;Park, Seong-Bae;Hwang, Bu-Hyun
    • The Transactions of the Korea Information Processing Society
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    • v.5 no.11
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    • pp.2763-2775
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    • 1998
  • In mobile computing environments, to efficiently use the narrow bandwidth of wireless networks a mobile host caches the data that are frequently accessed. But, because the cached data can be inconsistent with the data n a server due to the host mobility and the disconnection from a server, the usefullness of cached data may be losted. The traditional methods emphasize on the cache consistency and assume that broadcasting times are synchronized at all mobile supprot stations. In this paper, we propose a strategy to maintain cache consistency, which resolves the problems that be caused by the migration of mobile host. The proposed strategy has asynchronous broadcasting time and reduces the communication overhead caused by the synchronization. Also, by preventing the unnecessary messages transmitting from the mobile support station to a mobile host, this strategy can reduce the communication cost and use the narrow bandwidth of wireless networks efficiently.

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공유 데이터베이스 환경에서 고성능 트랜잭션 처리

  • 김신희;배정미
    • Proceedings of the Korea Association of Information Systems Conference
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    • 1997.10b
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    • pp.215-227
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    • 1997
  • 데이터베이스 공유 시스템(database sharing system)은 고성능의 트랜잭션 처리를 위한 시스템으로서, 별도의 메모리와 운영체제 그리고 데이터베이스 관리 시스템(DBMS)을 가진 처리 노드와 고속의 통신 시스템으로 구성된다. 공유 데이터는 다수의 DBMS에 의해 동시에 캐싱 될 수 있으므로 처리노드 간의 일관성 유지를 위해 동시성 제어(concurrency control)와 일관성 제어(coherency control) 기법이 필요하다. 본 연구에서는 동적 PCA 관 리 방식과 이를 위한 버퍼 무효화 기법을 제안한다. 제안된 동적 PCA 관리 방식은 시스템 환경의 변화에 대한 적응성을 제공한다. 또한 공유 데이터의 일관성 유지를 위한 세 가지의 버퍼 무효화 기법은 디스크 I/O 오버헤드와 메시지 전송량을 감소함으로써 동적 PCA 관리 를 효율적으로 지원할 수 있다.

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A Method for Maintaining Mobile Transaction Serializability using Lock Operation and Serialization Graph in Mobile Computing Environments (이동 컴퓨팅 환경에서 록 연산과 직렬화 그래프를 이용한 이동 트랜잭션의 직렬성 유지 방법)

  • Kim, Dae-In;Hwang, Bu-Hyeon;Hwang, Bu-Hyeon
    • Journal of KIISE:Software and Applications
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    • v.26 no.9
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    • pp.1073-1084
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    • 1999
  • 이동 컴퓨팅 환경에서 이동 호스트는 제한된 대역폭을 효율적으로 사용하고 이동 트랜잭션의 응답 시간을 향상시키기 위하여 캐쉬를 이용한다. 그리고 이동 호스트에 캐슁된 데이타가 이동 지구국에서 갱신되면 이동 호스트의 캐쉬 일관성을 유지하기 위하여 이동 지구국은 무효화 메시지를 방송한다. 그러나 이동 지구국에서 주기적으로 무효화 메시지를 방송하는 방법은 이동 트랜잭션의 빠른 처리를 위하여 이동 지구국으로부터 데이타를 즉시 캐슁하는 경우에 이동 트랜잭션의 직렬가능한 수행을 보장할 수 없는 경우가 발생한다. 본 연구에서는 캐슁된 데이타를 이용하여 이동 트랜잭션을 수행하는 경우에 록을 이용하여 이동 트랜잭션의 직렬가능한 수행을 보장하는 UCL-MT 방법과 록 관리 방법을 제안한다. 제안하는 UCL-MT 방법은 이동 트랜잭션을 완료하기 이전에 이동 트랜잭션이 접근한 데이타 정보를 이용하여 지구국에서 사이클을 탐지함으로써 이동 트랜잭션의 직렬가능한 수행을 보장한다. 또한 제안하는 록 관리 방법은 이용할 수 있는 대역폭의 크기에 따른 무효화 메시지 내용의 변화에 유연하게 적용될 수 있다. Abstract In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time of a mobile transaction. If the cached data in mobile host is updated at a mobile support station, the mobile support station broadcasts an invalidation message for maintaining the cache consistency of a mobile host. But when a mobile transaction accesses the data which is not in cache, if a mobile host caches the data immediately from a mobile support station for processing a mobile transaction rapidly, the method that a mobile support station broadcasts an invalidation message periodically, happens to the case that can not guarantee the serializable execution of a mobile transaction. In this paper, we propose the UCL-MT method and lock management method, as a mobile transaction is executed using cached data. Since, using the data a mobile transaction accessed, the UCL-MT method detects a cycle in a mobile support station before the completion of the mobile transaction, it guarantees the serializable execution of the mobile transaction. Also, proposing lock management method can be adapted flexibly at the change of invalidation message content, according to the available bandwidth.

Concurrency Control Method using the Asynchronous Data Broadcast in Mobile Computing Environments (이동 컴퓨팅 환경에서 비동기적 데이터방송을 사용한 동시성 제어 기법)

  • Ko Seung-Min;Kim Dae-In;Im Sun-Mo;Hwang Bu-Hyun
    • The KIPS Transactions:PartD
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    • v.12D no.1 s.97
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    • pp.21-30
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    • 2005
  • In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time. A server periodically broadcasts the update data for maintaining the cache consistency of a mobile host. However, a method for maintaining cache consistency using periodic invalidation report has a problem that defers the commit decision of a mobile transaction to guarantee its serializable execution. In this paper, we propose CCM-AD method that guarantees the serializable execution of a mobile transaction even in the case that it is executed using cached data. As CCM-AD method guarantees the serializable execution of mobile transactions by using the intersection between the data broadcast to mobile host and the data updated at server. Then the CCM-AD method can reduce the delay of commitment decision of a mobile transaction. Also our method can reduce the size of invalidation report.

A Strategy for Efficiently Maintaining Cache Consistency in Mobile Computing Environments of the Asynchronous Broadcasting, (비동기적 방송을 하는 이동 컴퓨팅 환경에서 효율적인 캐쉬 일관성 유지 정책)

  • 김대옹;박성배;김길삼;황부현
    • Journal of the Korea Society of Computer and Information
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    • v.4 no.3
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    • pp.78-92
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    • 1999
  • In mobile computing environments, to efficiently use the narrow bandwidth of wireless networks a mobile host caches the data that are frequently accessed. To guarantee the correctness of the mobile transaction, the data cached in a mobile host must be consistent with the data in a server. This paper proposes a new strategy which maintains cache consistency efficiently when the data cached in a mobile host are inconsistent with the data in a server by the mobility of the mobile host at the asynchronous mobile environment. In this strategy, the size of the invalidation message is relatively small and is independent of the number of data to be invalidated under conditions of variable update rates/patterns. So this strategy uses the narrow bandwidth of wireless networks efficiently and reduces the communication cost.

A Strategy using Updatable Message for Retaining the Cache Consistency in the Mobile Computing Environment (이동 컴퓨팅 환경에서 갱신가능 메시지를 이용한 캐쉬 일과성 유지 정책)

  • Park, Seong-Bae;Hwang, Bu-Hyun
    • The Transactions of the Korea Information Processing Society
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    • v.4 no.7
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    • pp.1694-1705
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    • 1997
  • In the future mobile computing environment, it will be generalized that a mobile host with portable Laptop of Palmtop accesses to database through wireless communication channel. For solving the problems which are caused from low bandwidth of wireless communication, mobile hosts cache the datum used frequently on them. Thus the mobile hosts must always retain the cache consistency for the correctness of the cached datum. the cache consistency is mainly affected from the unrestricted host mobility and the disconnection of the communication between mobile hosts and mobile support station. In this situation, the strategy to retain efficiently cache consistency is required. In this paper, we propose a strategy using updatable message for retaining the cache consistency, in the mobile computing environment, with replicated database supporting 2 phase commit protocol. This strategy makes use of a updatable message to resolve the cache consistency problem, since mobile host crosses the boundary of cell. In using of this updatable, it find out and cache only the update data of missing invalidation message. As a result, the proposed strategy utilizes network bandwidth efficiently because it is not need to delete all the cached datum with any datum change.

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Update Frequency Cache Consistency for Reducing Wait Time in Mobile Computing (이동 컴퓨팅 환경에서 대기 시간을 감소시키는 갱신 빈도 캐쉬 일관성 기법)

  • Lee, Chan-Seob;Kim, Dong-Hyuk;Baek, Joo-Hyun;Choi, Eui-In
    • The KIPS Transactions:PartD
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    • v.9D no.6
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    • pp.1017-1024
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    • 2002
  • According as mobile computing environment is generalized by development of wireless networking technology and communication device, mobile host uses local cache for extensibility and early response time. and reduction of limited bandwidth. This time, between mobile host and mobile support station cache need consistency interested person of done data accordingly much techniqueses propose. Existent consistency techniques because detection based techniqueses are used mainly and broadcast periodic invalid message considering frequent disconnection. However, these techniqueses increase abort step through increase or delay of transmission message number by accuracy examination of data. Therefore, because mobile host deletes cached data, and extensity are decreased. Techniques that is proposed in this paper did to perform refering update frequency about object that page request or when complete update operation happens to solve these problem. Therefore, have advantage that response is fast because could run write intention declaration or update by update frequency electively asynchronously when update operation consists and abort step decreases. Also, improved extensity running delete or propagation electively according to update frequency about periodic invalid message gone since disconnection.