• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2784-2790
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• 2015

The column-oriented database storage is a very advanced model for large-volume data transactions because of its superior I/O performance. Traditional data storages exploit row-oriented storage where the attributes of a record are placed contiguously in hard disk for fast write operations. However, for search-mostly data warehouse systems, column-oriented storage has become a more proper model because of its superior read performance. Recently, solid state drive using flash memory is largely recognized as the preferred storage media for high-speed data analysis systems. In this research, we propose a new transaction recovery scheme for a column-oriented database environment which is based on a flash media file system. We improved traditional shadow paging schemes by reusing old data pages which are supposed to be invalidated in the course of writing a new data page in the flash file system environment. In order to reuse these data pages, we exploit reused shadow list structure in our column-oriented shadow recovery(CoSR) scheme. CoSR scheme minimizes the additional storage overhead for keeping shadow pages and minimizes the I/O performance degradation caused by column data compression of traditional recovery schemes. Based on the results of the performance evaluation, we conclude that CoSR outperforms the traditional schemes by 17%.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.89-92
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• 2001

본 논문에서는 공간 데이터베이스 시스템의 공간 데이터 크기에 의한 선별적 회복 기법을 제안하고자 한다. 기존의 대용량 데이터베이스를 위한 회복 관리 기법에는 쉐도우 기법과 변형된 로그 기법이 쓰여지고 있다. 쉐도우 기법은 물리적 응집과 잠금 경쟁 문제가 있으며, 변형된 로그 기법은 공간 데이터의 가변 크기 특성에 대한 고려가 없기 때문에 디스크 입출력이 빈번히 발생하는 문제가 있다. 본 논문에서 제안하는 회복 기법은 공간데이터 크기에 따라 각각 다른 회복 기법을 적용하여, 로그 파일에 기록되는 로그의 양을 줄이며, 또한 트랜잭션 철회시 회복 연산으로 인한 시스템의 부하를 줄이는 장점을 갖는다.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.7
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• pp.149-156
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• 2020

All operating systems have privileged administrator accounts for efficient management. Dangerous or sensitive tasks or resources should be banned from normal users and should only be accessible by administrators. One example of this privilege is to reset a user's password when the user loses his/her password. In this paper, the privileges of the sudoer group, the administrator group of Linux Ubuntu, and the management system of the sudoer group were analyzed. We show the danger that a sudoer can use the privilege to change the password of other users, including other sudoers, and modify the log, and suggest a countermeasure to prevent the manipulation of shadow files as a solution to this. In addition, the proposed method was implemented and the possibility of practical use was confirmed with excellent performance.