• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1377-1389
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• 1998

Firm real time transactions on firm real-time database systems arc discarded when they miss their deadlines. as there is no value to completing them after they miss their deadlines. Several approaches that exploit the semantics of firm deadlines to improve the performance of firm real-time database systems have been proposed in the literature. They are based Oil locking or optimistic concurrency controL The performance comparisons of the two approaches differ with svstems load. In this paper. we develop a novel policy termed stop/resume deferred restart policy, and a concurrency control algorithm based on the policy (temled Altcmativc Version Concurrency Contro). When conflicts : due to Pliority) occur our algmithm maintains the immediately restarted VerSlOn as wpll as the stopped version of a transaction in order to use one of the two to meet the firm deadline. At last we show that our policy generates scrializable schedules and show tbat our algorithm performs better than the traditionally used method for wide ranges of the system load for firm deadline transaction.

• Journal of KIISE:Databases
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• v.32 no.6
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• pp.628-640
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• 2005

The XML is well accepted in several different Web application areas. As soon as many users and applications work concurrently on the same collection of XML documents, isolating accesses and modifications of different transactions becomes an important issue. When an XML document correctly corresponds to the rules laid out in a DTD or XML schema, it is also said to be valid. The valid XML document's validity should be guaranteed after the document is updated. The validation method mentioned above, however, results in lower degree of concurrency. For getting higher degree of concurrency and minimizing the range of the XML document validity, a new validation method based on a specific locking method is required. In this paper we propose the sequence group validation method for minimizing the range of the XML document validity. We also propose the boundary locking method for isolating accesses and modifications of different transactions while supporting the valid XML document's validity. Finally, the results of some experiments show the validation and locking methods increase the degree of transaction concurrency.

• Journal of Advanced Navigation Technology
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• v.12 no.4
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• pp.357-365
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• 2008

Broadcast is a efficient interactive method between a server and mobile clients via wireless channel and broadcast environments are incarnating as various applications. Most studies have been proposed in broadcast environments deal with read-only mobile transactions, many applications are emerging recently that need to manage the update transactions at mobile clients. So we propose a concurrency control for mobile transactions consisted mainly of update operations in broadcast environments. As an optimistic approach is applied for scheduling update transactions, repetitive aborts of update transactions are occur due to conflict between transactions. To solve this problem update transactions must have been executed with distributed manner, but unnecessary aborts are occur as well because of continuous restart. Thus, in this paper we propose a method that transactions are executed distributed manner and can avoid unnecessary aborts of update transactions. Proposed method has no unnecessary uplink and can save resources of mobile client.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.62-65
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• 2002

The locking is the most widely-used concurrency control mechanism for guaranteeing logical consistency of a database where a number of transactions perform concurrently. In this Paper, we propose a new method for lock management appropriate in main-memory databases. Our method chooses the partition, a fixed-sized container for records. as a unit of locking. and directly keeps lock information within the Partition itself. These make our method enjoy the following advantages: (1) it has freedom in controlling of the trade-off between the system concurrency and the lock processing overhead by considering the characteristics of given target applications. (2) it enhances the overall system performance by eliminating the hashing overhead, a serious problem occurred in the traditional method.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.304-314
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• 2005

In this paper, we propose a new phantom protection method for multi-dimensional index structures that uses multi-level grid technique. The proposed mechanism is independent of the types of multi-dimensional index structures, i.e., it can be applied to all types of index structures such as tree-based, file-based and hash-based index structures. Also, it achieves low development cost and high concurrency with low lock overhead. It is shown through various experiments that the proposed method outperforms existing phantom protection methods for multi-dimensional index structures.

• The KIPS Transactions:PartD
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• v.8D no.1
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• pp.24-31
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• 2001

In this paper, we present an advanced transaction scheduling protocol to improve the degree of concurrency and satisfy the security requirements for multilevel secure database. We adapted two-phase locking protocol, namely traditional syntax-oriented serializability notions, to multilevel secure database. Altruistic locking, as an advanced protocol, has attempted to reduce delay effect associated with lock release moment by use of the idea of donation. An improved form of altruism has also been deployed for extended altruistic locking OffiLl. This is in a way that scope of data to be early released is enlarged to include even data initially not intended to be donated. We also adapted XAL to multilevel secure database and we first of all investigated limitations inherent in both altruistic schemes from the perspective of alleviating starvation occasions for transactions in particular of short-lived nature for multilevel secure database. Our protocol is based on extended altruistic locking for multilevel secure database (XAL/MLS), but a new method, namely two-way donation locking for multilevel secure database (2DL!/-MLS), is additionally used in order to satisfy security requirements and concurrency. The efficiency of the proposed protocol was verified by experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.4
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• pp.1655-1673
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• 2018

Mobile computing environment is subject to the constraints of bounded network bandwidth, frequently encountered disconnections, insufficient battery power, and system asymmetry. To meet these constraints and to gain high scalability, data broadcasting has been proposed on data transmission techniques. However, updates made to the database in any broadcast cycle are deferred to the next cycle in order to appear to mobile clients with lower data currency. The main goal of this paper is to enhance the transaction performance processing and database currency. The main approach involves decomposing the main broadcast cycle into a number of sub-cycles, where data items are broadcasted as they were originally sequenced in the main cycle while appearing in the most current versions. A concurrency control method AOCCRBSC is proposed to cope well with the cycle decomposition. The proposed method exploits predeclaration and adapts the AOCCRB method by customizing prefetching, back-off, and partial backward and forward validation techniques. As a result, more than one of the conflicting transactions is allowed to commit at the server in the same broadcast cycle which empowers the processing of both update and read-only transactions and improves data currency.

• The KIPS Transactions:PartD
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• v.11D no.4
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• pp.809-822
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• 2004

In this paper, we propose a concurrency control algorithm based on R-tree for spatial database management system. The previous proposed algorithms can't prevent problem that search operation is to be blocking during update operations. In case of multidimensional indexes like R-tree, locking of update operations may be locked to several nodes, and splitting of nodes have to lock a splitting node for a long time. Therefore search operations have to waiting a long time until update operations unlock. In this paper we propose new algorithms for lock-free search operation. First, we develop a new technique using a linked-list technique on the node. The linked-list enable lock-free search when search operations search a node. Next, we propose a new technique using a version technique. The version technique enable lock-free search on the node that update operations is to be splitting.

• Journal of the Korea Society for Simulation
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• v.12 no.2
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• pp.13-24
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• 2003

In this study, we propose a scheduling analysis method of the Flexible management system using the transitive matrix. The Scheduling problem is a combination-optimization problem basically, and a complexity is increased exponentially for a size of the problem. To reduce an increase of a complexity, we define that the basic unit of concurrency (short BUC) is a set of control flows based on behavioral properties in the net. And we propose an algorithm to divide original system into some BUC. To sum up, we divide a petri net model of the Flexible management system Into the basic unit of concurrency through the division algorithm using the transitive matrix. Then we apply it to the division-scheduling algorithm to find an efficient scheduling. Finally, we verify its efficiency with an example.

• The KIPS Transactions:PartD
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• v.10D no.1
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• pp.1-12
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• 2003

Recently, there have been many indexing schemes for multimedia data such as image, video data. But recent database applications, for example data mining and multimedia database, are required to support multi-user environment. In order for indexing schemes to be useful in multi-user environment, a concurrency control algorithm is required to handle it. So we propose a concurrency control algorithm that can be applied to CBF (cell-based filtering method), which uses the signature of the cell for alleviating the dimensional curse problem. In addition, we extend the SHORE storage system of Wisconsin university in order to handle high-dimensional data. This extended SHORE storage system provides conventional storage manager functions, guarantees the integrity of high-dimensional data and is flexible to the large scale of feature vectors for preventing the usage of large main memory. Finally, we implement the web-based image retrieval system by using the extended SHORE storage system. The key feature of this system is platform-independent access to the high-dimensional data as well as functionality of efficient content-based queries. Lastly. We evaluate an average response time of point query, range query and k-nearest query in terms of the number of threads.