• 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.35 no.3
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• pp.257-271
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• 2008

Wireless broadcast environments has character that a number of mobile client can receive data streaming from central server no matter how they are so many. Because it is asymmetric bandwidth in that uplink and downlink bandwidth are different. This advantage helps wireless broadcast environments is used in many applications. These applications work almost read operation and need control concurrency using transaction unit. Previous concurrency control scheme in single channel is not adapted in multi channel environments because consistency of data are broken when a mobile client tunes in a broadcast cycle in a channel and then move into another channel and listen to different broadcast cycle with already accessed broadcast cycle. In this paper, we propose concurrency control for read-only mobile transactions in multiple wireless broadcast channel. First of all, we adapt index and data dedicated channel and propose LBCPC(Longest Broadcast Cycle Per Channel) as new unit of consistency. In index dedicated channel, it is repeatedly broadcasted data in same BCPC(Broadcast Cycle Per Channel) until LBCPC. And mobile transaction executes validation using control information every LBCPC. As a result, consistency of data is kept and average response time is shorter than one in single channel because waiting time for restart reduces. And as control information is broadcasted more frequently than in single channel, it is guaranteed currency about data accessed by transaction. Finally, according to the simulation result, we verify performance of our scheme in multi channel as comparing average response time with single channel.

• The Journal of the Korea Contents Association
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• v.6 no.9
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• pp.60-66
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• 2006

With the advances of wireless information technology, many application softwares such as ERP gradually has increased. But those application softwares have some serious problems such that performance degradation and concurrency control resulting from the limited bandwidth and unreliability of wireless communication, In this paper, as a solution to take around those limitations, we propose a middleware framework for wireless communication environments.

• Proceedings of the Korea Database Society Conference
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• 1995.12a
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• pp.132-142
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• 1995

Development in multimedia technology enhances Computer Supported Cooperative Work(CSCW) such as tole-conferencing and tole-education. These applications are also called groupware applications and usually composed of AM conferencing module and shared working space such as group editors. Through this shared working space users can present, manipulate and save common artifacts interactively. Since users are allowed to operate on common artifacts simultaneously, conflicts between user transactions are bound to happen and can cause unnatural effects on user interfaces. In this paper we reviewed these problems and presented common solutions to concurrency control problems. We also presented Coshed/SAS, a group editor, as an example of groupware applications and related concurrency control problems.

• The Transactions of the Korea Information Processing Society
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• v.1 no.2
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• pp.172-183
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• 1994

In the multidatabase systems(MDBS), local autonomy and global consistency are important issues. Global consistency could be maintained by a global concurrency control algorithm and a global recovery algorithm. In this thesis, we propose a global concurrency control algorithm to ensure local autonomy and to guarantee global serializability, and a global recovery algorithm which is possible to recover the multudatabase from any failures. The proposed global concurrency control algorithm uses bottom-up approach, based on three-level transaction processing model. It can produce a local history that the execution order of subtransactions is identical to their serialization order by using dummy-operations in the server when an indirect conflict is caused between subtransactions due to local transactions. At the global module, it can efficiently validate global serializability of global transactions by checking global serializability only for the global transactions which conflict with each other.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5B
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• pp.520-530
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• 2004

A multidatabase system (MDBS) is designed to provide universal access to distributed data across multiple autonomous, heterogeneous local database systems (LDBSs). In this paper, we propose a global concurrency control (GCC) algorithm in MDBS. The proposed GCC algorithm adopts the idea of message ordering in group communication messaging system. A necessary condition of GCC algorithm is that global transactions are serialized in the same order at all LDBSs that they execute. n all operations of a transaction are bundled in a single message and the message arrives at LDBSs in the same order using message ordering property, each LDBS can perform subtransactions in the same order. As a result, message ordering allows to determine easily the relative serialization order of global transactions, and then it can support a local autonomy without any information about the serialization order of transactions executing locally.

• 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 Internet Computing and Services
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• v.15 no.1
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• pp.63-71
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• 2014

Currently many non-traditional application areas such as artificial intelligence and web databases require advanced modeling power than the existing relational data model. In those application areas, object-oriented database (OODB) is better data model since an OODB can providemodeling power as grouping similar objects into class, and organizing all classes into a hierarchy where a subclass inherits all definitions from its superclasses. The purpose of this paper is to develop an OODB concurrency control scheme dealing with multiple inheritance. The proposed scheme, called Multiple Inheritance Implicit Locking (MIIL), is based on so-called implicit locking. In the proposed scheme, we eliminate redundant locks that are necessary in the existing implicit locking scheme. Intention locks are required as the existing implicit locking scheme. In this paper, it is shown that MIIL has less locking overhead than implicit locking does. We use only OODB inheritance hierarchies, single inheritance and multiple inheritance so that no additional overhead is necessary for reducing locking overhead.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.473-482
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• 2001

Integrated heterogeneous database systems provide the unified interface for users and applications today in order to access the underlying diverse data sources located in different sites. The multiple heterogeneous data sources have the different and specialized data structures and transaction processing capabilities. Because of local autonomy, the local system does not have the capability of cooperation to control the global transaction. Hence designing the global transaction manager with supporting the global serializability is difficult task. To resolve the well-known indirect conflict, we define the global transaction model by using the characteristics of global integrity constraints. And then we propose the site-locking operation and its protocol to manage the global transaction. The correctness and analysis of our site-locking protocol is proved and performance gain over the related other methods is also estimated in this paper.