• Journal of KIISE:Databases
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• v.31 no.2
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• pp.140-149
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• 2004

Data broadcast has received much attention as a very efficient method for disseminating data items in mobile environment with large number of mobile clients. In this approach, a database server periodically and continuously broadcasts data items through wireless channels and clients perform read-only transactions by accessing necessary data items from the air. While broadcasting, the server must also process update transactions on the database, which raises an obstacle for client's accessing consistent data. In this research, we propose a new algorithm SCDSC(Serialization Checking with DirtySet on Commit) which is an alternative for solving the concurrency control problem efficiently. The SCDSC is a kind of optimistic concurrency control in that a client checks the consistency of data using a DirtySet as a part of data broadcast when it commits its transaction. In each broadcast cycle, the server updates and disseminates the DirtySet with newly changed data items for last few cycles in the sliding window approach. We perform an analysis and a simulation study to evaluate the performance of our SCDSC algorithm in terms of data consistency and data currency.

• The Transactions of the Korea Information Processing Society
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• v.3 no.6
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• pp.1418-1432
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• 1996

In addition t improved availability, replication of data can enhance performance of distributed real-time transaction processing system by allowing transactions initiated at multiple node to be processed concurrently. To satisfy both the consistency and real-time constraints, it is necessary to integrate concurrency control and atomic commitment protocols with time-driven scheduling methods. blocking caused by existing concurrency control protocols is incompatible with time-driven scheduling because they cannot schedule transactions to meet given deadlines. To maintain consistency of replicated data and to provide a high degree of schedulability and predictability , the proposed time-driven scheduling methods integrate optimistic concurrency control protocols that minimize the duration of blocking and produce the serialization by reflecting the priority transactions. The atomicity of transactions is maintained to ensure successful commitment in distributed environment. Specific time-driven scheduling techniqueare discussed, together with an analysis of the performance of this scheduling.

• Journal of KIISE:Databases
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• v.32 no.1
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• pp.100-110
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• 2005

The update transactions to be executed in spatial databases usually have been known as interactive and long duration works. To improve the parallelism of concurrent updates, it needs multiple transactions concurrently update a large spatial object which has a spatial extensions larger than workspace of a client. However, under the existing locking protocols, it is not possible to concurrently update a large spatial object because of conflict of a write lock This paper proposes a partial locking scheme of enabling a transaction to set locks on parts of a big object. The partial locking scheme which is an exclusive locking scheme set by user, acquires locks for a part of the big object to restrict the unit of concurrency control to a partial object of a big object. The scheme gives benefits of improving the concurrency of un updating job for a large object because it makes the lock control granularity finer.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.631-639
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• 1996

In this paper we discuss the elements which must be considered for collaboration- aware application design and their effcets on user interfaces. Collaboration-aware applications have inter-user and user/system interaction features besides generic real-time distribution system features and this restricts the design freedom with the requirement of consistent user interfaces. Programmers, therefore, must provide uniform and logically consistent user interfaces to user and, for this end, they should consider main design features such as concurrency control algorithms, system topology and object replication scheme. Among the design factors concurrency control algorithms have relatively significant impact on user interfaces and we consider the impact of concurrency control agorithms along with that of thesystem to pologyand the objectreplication scheme. Coshed/SAS, a groupeditor, is given as an example of application of the factors.

• Journal of Korea Multimedia Society
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• v.21 no.2
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• pp.232-241
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• 2018

Operational Transformation (OT) algorithms for real-time collaborative editing systems are becoming increasingly important due to the increased demand for collaborative data processing. The operational transformation algorithm is a technique for real-time concurrency control and consistency maintenance with non-locking technique, and many studies have been conducted to overcome three issues of convergence, causality-prevention, and intention-prevention. However, previous work has the disadvantage of wasting memory by storing all operations that occurred during an edit operation in the history buffer to solve this problem. Therefore, we propose a memory-saving real-time collaborative editing system that maintains a constant memory space and concurrency control through a method of applying the valid-time to each user-generated operation in order to reduce memory waste. This system prevents long-term memory occupation of client-generated operations, thus it reduces the space and time complexity even with low-rate of collaboration work, so that the performance degradation avoids.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.805-811
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• 2003

System test is an important factor in the development process of good quality complex software in time, ensuring user requirements. Transaction processing module of database management systems schedules multiple transactions effectively and ensures that each transaction preserves data consistency. In this paper, we propose automatic functional testing techniques which ensure systematically that the implemented concurrency control function confirms to its requirements. The proposed testing technique tests functions of concurrency control module based on scenario without user intervention, and displays the result of functional testing. Finally, we utilize the proposed functional testing technique in the testing process of a database management system.

• Journal of Information Processing Systems
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• v.14 no.2
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• pp.499-509
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• 2018

Recently, hybrid transactional memory (HyTM) has gained much interest from researchers because it combines the advantages of hardware transactional memory (HTM) and software transactional memory (STM). To provide the concurrency control of transactions, the existing HyTM-based studies use a bloom filter. However, they fail to overcome the typical false positive errors of a bloom filter. Though the existing studies use a global lock, the efficiency of global lock-based memory allocation is significantly low in multi-core environment. In this paper, we propose an efficient hybrid transactional memory scheme using near-optimal retry computation and sophisticated memory management in order to efficiently process transactions in multi-core environment. First, we propose a near-optimal retry computation algorithm that provides an efficient HTM configuration using machine learning algorithms, according to the characteristic of a given workload. Second, we provide an efficient concurrency control for transactions in different environments by using a sophisticated bloom filter. Third, we propose a memory management scheme being optimized for the CPU cache line, in order to provide a fast transaction processing. Finally, it is shown from our performance evaluation that our HyTM scheme achieves up to 2.5 times better performance by using the Stanford transactional applications for multi-processing (STAMP) benchmarks than the state-of-the-art algorithms.

• The Journal of the Korea Contents Association
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• v.10 no.7
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• pp.115-121
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• 2010

It always must guarantee preceding process of the transaction with the higher priority in real-time database systems. The pessimistic concurrency control method resolves a conflict through aborting or blocking of a low priority transaction. However, if a high priority transaction is eliminated in a system because of its deadline missing, an unnecessary aborting or blocking of a low priority transaction is occurred. In this paper, the proposed method eliminates a transaction that is about to miss its deadline. And it prevents needless wastes of resources and eliminates unnecessary aborting or blocking of a low priority transaction. It is shown through the performance evaluation that the proposed method outperforms the existing methods in terms of the deadline missing ratio of transactions.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.41-48
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• 2005

In this thesis, we propose a concurrency control scheme which schedules global transactions in multidatabase systems Unlike other scheme which commit global transactions as soon as they have finished their execution, this scheme has attempted to delay them if their exist another global transactions that should be proceeded. Owing to the deferred commitment, the number of global restarts could be greatly reduced. This scheme's performance gain increased through simulations in case more than one LDBS employ timestamp ordering(TO) as a local concurrency control scheme.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.251-254
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• 2003

In order for multidimensional infer structures to be integrated into an existing database management system, proper concurrency control methods that guarantee all isolation levels supported by the database management system. Several concurrency control methods have been proposed. They ran be classified into predicate locking based methods and granular locking based methods. Most of them are difficult to implement and ran not be applied to non-tree structured index structures. In this paper, we propose a new concurrency control method that guarantee all isolation levels. It is easy to implement and can be applied to any type of index structures. We implement the proposed method and existing methods, and perform various experiments to show the superiority of the proposed algorithm.