Papers by Keyword: Concurrency Control

Abstract: For the lack of adaptability about the existing concurrency control algorithms, adaptive decision concurrency control algorithm is proposed. ADCC algorithm divides concurrency control process into two phases in: execution authorizing phase and strategy selecting phase. In execution authorizing phase, algorithm compares statistics and effectiveness of transactions to determine the execution order of conflict transactions. In strategy selecting phase, according to transactions’ read/write status and current conflict rate, algorithm selects optimistic/pessimistic conflict resolution strategy adaptively. Such selection mechanism makes ADCC algorithm have high efficiency no matter database system is busy or idle. Simulation experiment proves that ADCC algorithm this paper proposed is superior to classical strict two phases locking algorithm and hybrid concurrency control. So ADCC algorithm performs well in the period of concurrency control.

Abstract: This paper presents a new distributed index tree named RDB⁺-Tree and a concurrency control algorithm named VTC-RDB⁺. In RDB⁺-Tree, the leaf node is organized for a hash list. The principle of VTC-RDB⁺ algorithm can be established by utilizing multiple elements which are in favor of concurrency control and by combining with version and time control method. Theoretical analysis and experimental results show that the RDB⁺-Tree index tree and VTC-RDB⁺ algorithm can effectively enhance the query and updating performance of the massive data in the distributed circumstance.

Abstract: Currently, the embedded real-time database is widely applied in the embedded system and plays an important role. But on account of being mainly applied to the most important fields such as Communication, Spaceflight and Military as a key task control management, errors by it often results in irreversible fatal losses. Therefore, it is necessary to analyze the embedded real-time database key characteristics and test. This paper, by researching the characteristics, architecture and implementation technique of the embedded real-time database, analyzes its key properties including real-time transaction processing, concurrency control, recovery management, etc., and finally proposes applicable testing strategy and methods which have been proved in the actual test, being as a technique to evaluate the performance of the embedded real-time database.

Abstract: Alternative and compensation are not only two basic characteristics of the real-time transaction but also the body of the concurrency control. At the same time, new problems are brought. AC-Based OCC-FV protocol associates alternative and compensation with optimistic concurrency control protocol OCC-FV. For each transaction in accepted queue, an alternative which causes no conflict can be chosen to join the ready queue as soon as possible. This is just a kind of ideal circumstance. If the conflict is inevitable, it is necessary to choose a suitable alternative to join the concurrency control, but also ensures the system to be in a safe state when conflicts take place. In conflict resolution, the optimistic concurrency control protocol OCC-FV is extended in combination with the compensation characteristic, when the transaction failed, immediate dispatch of corresponding compensation transactions is taken to prevent the system from disaster.

Abstract: Based on topological graph theory, collaboration technique and other relevant theory, this paper carry out the research of exploring a technical path to solving the conflict of concurrency in CVM, Under the circum stances of conforming to logic and topological relationship , the attributes of timing sequence are studied emphatically, following the deeply analysis quantitatively and qualitatively, then the mathematical expression of predicted retardation and the control strategy are put forward, which builds a fair and friendly negotiation mechanism for occurrence priority distribution. Finally the OOT (Object Oriented Technology) based programming structure and realization means of the strategy are given in this paper. What elaborated in this paper has certain engineering and application value for the design of complicated virtual maintains system , conflict resolution of concurrency and the application of collaboration technique etc.

Abstract: In allusion to the transaction trait of the object-oriented mobile real-time database in the biomedical information service system, the new concurrency control communications protocol (PAI-OM-2PL) is put up with the fusion of common object two stages lock protocol (2PL) and concurrency control communications protocol (PAI-2PL) of traditional mobile real-time nested transaction. The aim of proposing this new communications protocol in the biomedical information service system is to give full play to transaction semanteme, can earlier release lock with using open nested transaction model. The performance of PAI-OM-2PL was tested on the object-oriented database (db4o) in the biomedical information service system, at the same time we simulate mobile computing setting. The result is that the performance is enhanced by using the new communications protocol in some surroundings.

Abstract: In the article a new concurrency control protocol for real-time database (RTCC) is proposed. The protocol based on the traditional speculative concurrency control protocol (SCC). It dynamically establish the maximum of shadow to reasonably use the resources of system and add the quasi-commit phase to avoid many unnecessary restarting and enhance the concurrency of transaction. The theory of Petri net proof and results of experiment show that this protocol is feasible and effective , and it can meet the needs of real-time transaction. Speculative Concurrency Control is suitable especially for real-time database[1]. On the one hand, SCC is similar to PCC, to detect potentially harmful conflict as early as possible, so as to start a replacement schedule, thereby increasing the opportunities for transactions to meet time limits. On the other hand, SCC is similar to OCC, it allows the concurrency of conflict transaction and, therefore, avoids unnecessary matters that may affect the timely submission of delay. As a result, it alleviates the congestion problems and PCC restart OCC's problems, in order to better meet the transaction deadline. Based on the fact above mentioned, we propose a suitable real-time database concurrency control protocol [2,3] (RTCC: Concurrency Control protocol for Real-Time). The protocol of the SCC protocol on the traditional basis with a series of improvements can avoid a large number of unnecessary transaction restart and improve concurrency. Finally, by Petri net theory it can be proved feasible and correct.

Abstract: The model of flow press servo valve is built in this paper, during building the model, the author emphatically analyses the flow equation and force (torque) balance equation of every part of the valve, at the same time, all levels sub-models are organic combined according to power flow direction, signal flow direction of elements and causality, then we get the bond graph model of the flow press servo from this way. Adapting flow press servo valve and flow servo valve to concurrently control load system has its great advantage in restraining the superfluous force of the electro-hydraulic load simulator system, the performance such as load precision of system is enhanced greatly according to this method. Based on the system bond graph model, and by comparing the simulation curves and experiment curves, we can know that the simulation curves basically tally with the experiment curves, the bond graph models are validated right, which are flow press servo valve bond graph model and double valves concurrently control the electro-hydraulic load simulator system bond graph model. Simultaneity, the bond graph models in this paper take on generality, they are can be used on other aspects, such as other valve controlling cylinder system simulation, design and control strategy theory research.