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데이타베이스 공유 환경에서 분산 동시성 제어를 위한 캐쉬 일관성 기법
김신희,류명춘,박정량 한국정보시스템학회 1998 情報시스템硏究 Vol.7 No.2
In Database sharing system, since multiple nodes may be simultaneously cached a page, cache coherency must be ensured so that every node can always access the latest version of pages. In this paper, we propose efficient cache coherency schemes in DBSS, where the database is logically partitioned using primary copy authority to reduce locking overhead. The proposed schemes can improve performance by reducing the disk I/O overhead and the message overhead due to maintaining cache coherency. Furthermore, they can show good performance when database workloads are varied dynamically. In this paper, we have proposed two cache coherency schemes such as DPCA_P and DPCA_U in the DBSS. The proposed schemes can reduce the disk I/O overhead and the communication overhead of conventional cache coherency scheme (SPCA) by reallocating PCA dynamically. Specifically, DPCA_P reallocates PCA when a page is replaced from the local buffer of PCA node. Hence, DPCA_P may alleviate the problem of excessive page faults of SPCA, since the replaced page need not be written to disk if another node caches the page. DPCA_U reallocates PCA when a node tries to update a page by requesting X lock to PCA node. This means that DPCA_U does not require the page transfer at transaction commit since an updating node becomes a new PCA node. We have explored the performance of DPCA_P and DPCA_U under a wide variety of database workloads and system configurations. The basic results obtained from the experiments can be summarized as follows. If the access pattern of transaction shows a low degree of locality of references, DPCA_P and DPCA_U outperform SPCA about 20% and 10%, respectively. However, the degree of performance improvements is reduced significantly when the locality of references is high. Note that providing good performance at low degree of locality of references is very promising, since in most. DBSS applications the degree of locality of references are about 30%. If the number of participating nodes are not large, DPCA_U performs better than SPCA even though all nodes have the same data access skew. However, as the number of nodes are increased, DPCA_U is outperformed by SPCA due to frequent PCA reallocations.
박재성,박주태,박정량,Park, Jae-Sung,Park, Ju-Tae,Park, Jung-Rang 한국조명전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.4
The effects of the addition of either monoclinic $ZrO_2(ZrO_2(m))$ or tetragonal $ZrO_2(ZrO_2(t))$ containing 5.35[wt%] $Y_2O_3$ on the physical properties and electrical conductivity of $Al_2O_3$ were investigated. The addition of $ZrO_2$(m) and $ZrO_2$(t) increased sintered density of $Al_2O_3$. The Vickers hardness also increased as addition of $ZrO_2$(t) increased going through a maximum at 20[wt%] and the hardness of the specimens was found to be dependent on the sintered density. The addition of $ZrO_2$(t) improved the hardness of $Al_2O_3-ZrO_2$ systems and the $ZrO_2$(m) addition showed the better effect on the thermal shock property of $Al_2O_3-ZrO_2$ systems than that of the $ZrO_2$(t) addition. Above 15[wt%] addition of $ZrO_2$(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of $ZrO_2$(m). 단사정 $ZrO_2(ZrO_2(m))$ 또는 $Y_2O_3$를 5.35[wt%] 첨가한 정방정 $ZrO_2(ZrO_2(t))$를 $Al_2O_3$에 첨가하여 물리적 및 전기전도도의 영향을 연구하였다. $ZrO_2$(m)과 $ZrO_2$(t)의 첨가는 $Al_2O_3$의 소결밀도를 증가시켰다. $ZrO_2$(t)의 첨가함에 따라 비커스 경도 또한 증가했으며, 그 량이 20[wt%]에서 최대가 되었다. 시편의 경도는 소결 밀도에 의존함을 알 수 있었다. $Al_2O_3-ZrO_2$계의 경도는 $ZrO_2$(t)의 첨가에 의해 개선되었고, $ZrO_2$(m)의 첨가가 $ZrO_2$(t)의 첨가보다 $Al_2O_3-ZrO_2$계의 열충격 특성에는 더 많은 영향을 받음을 알 수 있었다. 15[wt%] 이상의 $ZrO_2$(t) 첨가에서 인가전압이 증가 함에 따라 점차로 전기전도도가 증가 하였으나, $ZrO_2$(m)의 첨가에서는 영향이 없었다.
ZrO₂(m)-Al₂O₃/ZrO₂(t)-Al₂O₃ 세라믹스의 제조와 물리적 특성
박재성(Jae-Sung Park),박주태(Ju-Tae Park),박정량(Jung-Rang Park) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.4
단사정 ZrO₂(ZrO₂(m)) 또는 Y₂O₃를 5.35[wt%] 첨가한 정방정 ZrO₂(ZrO₂(t))를 Al₂O₃에 첨가하여 물리적 및 전기전도도의 영향을 연구하였다. ZrO₂(m)과 ZrO₂(t)의 첨가는 Al₂O₃의 소결밀도를 증가시켰다. ZrO₂(t)의 첨가함에 따라 비커스 경도 또한 증가했으며, 그 량이 20[wt%]에서 최대가 되었다. 시편의 경도는 소결 밀도에 의존함을 알 수 있었다. Al₂O₃-ZrO₂계의 경도는 ZrO₂(t)의 첨가에 의해 개선되었고, ZrO₂(m)의 첨가가 ZrO₂(t)의 첨가보다 Al₂O₃-ZrO₂계의 열충격 특성에는 더 많은 영향을 받음을 알 수 있었다. 15[wt%] 이상의 ZrO₂(t) 첨가에서 인가전압이 증가 함에 따라 점차로 전기전도도가 증가 하였으나, ZrO₂(m)의 첨가에서는 영향이 없었다. The effects of the addition of either monoclinic ZrO₂(ZrO₂(m)) or tetragonal ZrO₂(ZrO₂(t)) containing 5.35[wt%] Y₂O₃ on the physical properties and electrical conductivity of Al₂O₃ were investigated. The addition of ZrO₂(m) and ZrO₂(t) increased sintered density of Al₂O₃. The Vickers hardness also increased as addition of ZrO₂(t) increased going through a maximum at 20[wt%] and the hardness of the specimens was found to be dependent on the sintered density. The addition of ZrO₂(t) improved the hardness of Al₂O₃-ZrO₂ systems and the ZrO₂(m) addition showed the better effect on the thermal shock property of Al₂O₃-ZrO₂ systems than that of the ZrO₂(t) addition. Above 15[wt%] addition of ZrO₂(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of ZrO₂(m).