• The KIPS Transactions:PartC
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• v.12C no.3 s.99
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• pp.443-448
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• 2005

Efficient using of the web cache is becoming important factors that decide system management efficiency in the web base system. The cache performance depends heavily on the replacement algorithm which dynamically selects a suitable subset of objects for caching in a finite cache space. In this paper, the web caching algorithm is proposed for the efficient operation of the web base system. The algorithm is designed based on a divided scope that considered size reference characteristic and heterogeneity on web object. With the experiment environment, the algorithm is compared with conservative replacement algorithms, we have confirmed more than $15\%$ of an performance improvement.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.301-303
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• 2001

현재 무선단말기 보급의 확대와 시간과 공간의 제약을 뛰어넘는 장점으로 무선 인터넷 환경이 급속도로 발전하고 있다. 그러나, 본 논문의 연구 분야인 모바일 지리정보 시스템(Mobile Geographic Information System)에서 무선인터넷을 통하여 실시간 지리 정보를 얻기 위해 사용자의 무선단말기와 서버 사이에 빈번한 데이터 송수신이 이뤄져야 하며 데이터의 빠른 변화를 수용해야 한다. 그러나, 아직 현저히 낮은 대역폭을 가진 채널을 통해 통신하며, 비싼 이용 요금과 오류로 인한 자발적 또는 비자발적 연결 끊김 현상 등은 서비스 제공에 한계를 가진다. 그러므로 본 논문에서는 이동 컴퓨팅 환경의 연구를 통해 연결 끊김 현상에서도 클라이언트의 지속적인 서비스 운영을 위한 비연결 연산으로 의미론적 캐시 기법과 캐시 교체 전략에 대해 알아보며, 본 논문에서는 Layer와 Region을 고려한 의미론적 캐싱 기법을 제안하여 무선 환경에서 동적인 지도서비스를 위한 기법을 제시하였다. 이 연구를 통해 아직 많은 한계를 지닌 무선인터넷 환경에서 지리정보뿐 아니라 위치기반의 다양한 서비스 분야에 응용될 수 있으리라 기대된다.

• 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.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.9
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• pp.435-444
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• 2007

Caching web pages is an important part of web infrastructures. The effects of caching service are even more pronounced for wireless infrastructures due to their limited bandwidth. Medium to large-scale infrastructures deploy a cluster of servers to solve the scalability problem and hot spot problem inherent in caching. In this paper we present scheduling scheme based on cache utilization in a wireless internet proxy server cluster environment. The proposed method uses cache utilization for distributing evenly client requests to a cluster of cache servers and solving hot spot problem. We have implemented our approach and performed various experiments using publicly available traces. Experimental results on a cluster of 16 cache servers demonstrate that the proposed hashing method gives 45% to 114% Performance improvement over other widely used methods while addressing the hot spot problem.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1390-1403
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• 1998

Database sharing system (DSS) refers to a system for high performance transaction processing. In DSS, the processing nodes are locally coupled via a high speed network and share a common database at the disk level. Each node has a local memory, a separate copy of operating system, and a DB'\fS. To reduce the number of disk accesses, the node caches database pages in its local memory buffer. However, since multiple nodes may be simultaneously cached a page, cache consistency must be cnsured so that every node can always access the'latest version of pages. In this paper, we propose efficient cache consistency schemes in DSS, where the database is logically partitioned using primary copy authority to reduce locking overhead, The proposed schemes can improve performance by reducing the disk access overhead and the message overhead due to maintaining cache consistency, Furthermore, they can show good performance when database workloads are varied dynamically.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.1
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• pp.40-47
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• 2009

Recently, dynamic proxy caching has been proposed on the distributed environment so that media objects by user's requests can be served directly from the proxy without contacting the server. However, it makes caching challenging due to multimedia large sizes, low latency and continuous streaming demands of media objects. To solve the problems caused by streaming demands of media objects, this paper has been proposed the grouping scheme with fuzzy filtering based on partition and mapping. For partition and mapping, this paper divides media block segments into fixed partition reference block(R$_f$P) and variable partition reference block(R$_v$P). For semantic relationship, it makes fuzzy relationship to performs according to the fixed partition temporal synchronization(T$_f$) and variable partition temporal synchronization(T$_v$). Simulation results show that the proposed scheme makes streaming service efficiently with a high average request response time rate and cache hit rate and with a low delayed startup ratio compared with other schemes.

• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.63-73
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• 2003

Today, in exponential growth of internet, the importance of file caching which could reduce the sun load, the volume of network traffic, and the latency of response has emerged. Actually, in one network, the traffic has reduced by using the cache and this means that file caching can improve the internet environment by cost a fraction of link upgrades. In this paper, we address a dynamic cache group configuration policy, to solve the scalable problem. The simulation result shows that the cache group using our proposal policy reduces the latency of response time and it means that out cache group configuration is more scalable than the static cache configuration.

• Journal of Internet Computing and Services
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• v.9 no.3
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• pp.141-158
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• 2008

In this paper, we developed the GML Map Server which visualized the map based on GML as international standard for exchanging the common format map and for interoperability of GIS information. And also, it should transmit effectively GML map into the mobile device by using dynamic map partition and caching. It manages a partition based on the visualization area of a mobile device in order to visualize the map to a mobile device in real time, and transmits the partition area by serializing it for the benefit of transmission. Also, the received partition area is compounded in a mobile device and is visualized by being partitioned again as four visible areas based on the display of a mobile device. Then, the area is managed by applying a caching algorithm in consideration of repetitiveness for a received map for the efficient operation of resources. Also, in order to prevent the delay in transmission time as regards the instance density area of the map, an adaptive map partition mechanism is proposed for maintaining the regularity of transmission time. GML Map Server can trace the position of mobile device with WIPI environment in this paper. The field emulator can be created mobile devices and mobile devices be moved and traced it's position instead of real-world. And we developed POIM(POI Management) for management hierarchically POI information and for the efficiency POI search by using the individual tagging technology with visual interface.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.3
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• pp.193-204
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• 2006

In most existing distributed Web systems, incoming requests are distributed to servers via Domain Name System (DNS). Although such systems are simple to implement, the address caching mechanism easily results in load unbalancing among servers. Moreover, modification of the DNS is necessary to load considering the server's state. In this paper, we propose a new dynamic load balancing method using dynamic DNS update and round-robin mechanism. The proposed method performs effective load balancing without modification of the DNS. In this method, a server can dynamically be added to or removed from the DNS list according to the server's load. By removing the overloaded server from the DNS list, the response time becomes faster. For dynamic scheduling, we propose a scheduling algorithm that considers the CPU, memory, and network usage. We can select a scheduling policy based on resources usage. The proposed system can easily be managed by a GUI-based management tool. Experiments show that modules implemented in this paper have low impact on the proposed system. Furthermore, experiments show that both the response time and the file transfer rate of the proposed system are faster than those of a pure Round-Robin DNS.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.51-53
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• 2012

스마트폰과 같은 가상 메모리 환경의 임베디드 시스템은 메인 메모리의 제약과 다양한 응용프로그램들이 동시에 수행되어지기 때문에, 스왑 인/아웃(swap in/out)이 빈번히 일어난다. 스왑 비용은 메인 메모리에서 데이터를 사용하는 것보다 많은 시간이 걸려 이를 줄이기 위해 고속스왑장치를 사용한다. 이 때 기존 페이징에서 고려되지 않았던 코드 페이지를 스왑대상에 포함한다면, 빈번히 재시작이 일어나는 프로그램의 재기동 시간을 단축할 수 있을 것이다. 본 논문에서는 고속스왑장치를 사용하여 스왑비용을 낮추고, 자주 사용하는 코드를 동적으로 확인하여 코드페이지를 스왑대상에 포함시키는 방법을 제시한다. 이 기법의 효과를 확인하기 위해 멀티미디어 프로그램의 재기동 동작 시, 메모리 접근 정보를 트레이스(trace)하여 보조기억장치의 읽기 시간 감소를 확인하였다.