The problem of long transactions is a significant problem in spatial database. The checkout mechanism and multi version mechanism are two kind methods of solving the problem of long transactions. In this paper, we pre...The problem of long transactions is a significant problem in spatial database. The checkout mechanism and multi version mechanism are two kind methods of solving the problem of long transactions. In this paper, we present a Shallow Version Management mechanism to realize multi version mechanism in spatial database. And we introduced a increment storage and dynamic version views building method to improve efficiency of storing and consulting. We also illuminate how to resolve the problem of long transaction concurrency control in spatial database by using multi version mechanism. At the end of this paper, we introduce some required means to version management in spatial database, like converge, compress and delete.展开更多
The data model of WHYMX complicates transaction management. Traditional locking method is not powerful enough to solve the new problem of concurrency control of WHYMX's transaction. This paper presents a number of...The data model of WHYMX complicates transaction management. Traditional locking method is not powerful enough to solve the new problem of concurrency control of WHYMX's transaction. This paper presents a number of concurrency control algorithms based on the extended locking method.展开更多
This paper presents a practical concurrency control mechanism - ObjectLockingin OODBMS. Object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classe...This paper presents a practical concurrency control mechanism - ObjectLockingin OODBMS. Object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classes. Bythe properties of parallelity and coatativity between high level operations,proper lock modes for each operation are desigued and the compatibility matrixis constructed. With these lock modes, phatoms are kept away from databasesand a high degree of concurrency is achieved.展开更多
Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of sa...Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real time databases in most cases. On the other hand, relaxed serializability including epsilon serializability and similarity serializability can allow more real time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real time databases can be greatly improved.展开更多
An integrated method for concurrency control in parallel real-time databases has been proposed in this paper. The nested transaction model has been investigated to offer more atomic execution units and finer grained c...An integrated method for concurrency control in parallel real-time databases has been proposed in this paper. The nested transaction model has been investigated to offer more atomic execution units and finer grained control within in a transaction. Based on the classical nested locking protocol and the speculative concurrency control approach, a two-shadow adaptive concurrency control protocol, which combines the Sacrifice based Optimistic Concurrency Control (OPT-Sacrifice) and High Priority two-phase locking (HP2PL) algorithms together to support both optimistic and pessimistic shadow of each sub-transaction, has been proposed to increase the likelihood of successful timely commitment and to avoid unnecessary replication overload.展开更多
This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are propos...This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are proposed in the paper. The ideas of single queue scheduling(SQS) and dual queue scheduling (DQS) are proposed and the algorithm and the performance evaluation for these two scheduling are presented in some paper. This paper describes a new idea of thescheduling for MGL, compatible requests first (CRF). Combining the new idea with SQS and DQS,we propose two new scheduling algorithms called CRFS and CRFD. After describing the simulationmodel, this paper illustrates the comparisons of the performance among these four algorithms. Asshown in the experiments, DQS has better performance than SQS, CRFD is better than DQS, CRFSperforms better than SQS, and CRFS is the best one of these four scheduling algorithms.展开更多
In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can e...In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.展开更多
This paper covers the transaction management of C-POREL, i. e. the distributed rela-tional data base management system on a microcomputer network. Presented in the pa-per are the concurrency control strategy of transa...This paper covers the transaction management of C-POREL, i. e. the distributed rela-tional data base management system on a microcomputer network. Presented in the pa-per are the concurrency control strategy of transactions in C-POREL, the mechanism ofthe local and global recovery, the reliable state control protocol RSC for getting the ro-bustness of the network and the protocol for processing distributed multisite transactions,and the outline of the architecture of the transaction manager TM of C-POREL.展开更多
We have considered a method called Enhanced Rollback Migration Protocol, which potentially has the effects of compressing the period of compensations in a long-lived transaction, since before. In general, a compensati...We have considered a method called Enhanced Rollback Migration Protocol, which potentially has the effects of compressing the period of compensations in a long-lived transaction, since before. In general, a compensation transaction can recover an irregular status of a long-lived transaction into the original status without holding unnecessary resources by making its consistency tentatively loose. However, it has also been pointed out that there is a difficulty of maintaining the isolation between a pair of transactions when executed in parallel. In particular, this could be more prominent under modernized scalable cloud environments. Thus, there is a proposal for concurrency control for the service level. However, there is still another risk that more computer resources will be consumed than actually necessary and an unnecessary stagnation of the processing will be caused if concurrency control is naively applied without careful consideration. Therefore, we need to implement a functionality which can optimize the processing of a long-lived transaction by selecting a suitable method between concurrency control and compensation transactions. In this paper, we propose a method in which optimistic concurrency control is applied for long-lived transactions. Furthermore, a pair of verification phases is carried out. At the beginning from a safe point, an attempt of verification is done. Then if the difficulty of isolation on a long-lived transaction executed under a competitive situation is estimated, concurrency control for the service level is applied. Alternatively, a long-lived transaction without any concurrency control is executed. At the next reachable safe point, another attempt of verification is performed. Then if a failure of serialization is detected, a set of compensation transactions is invoked to recover the original long-lived transaction by returning to the first safe point. We evaluated this approach by using numerical simulations and confirmed the basic features. This approach can realize optimizing and enhancing the performance of a long-lived transaction. We regard this approach applicable even to the modernized scalable cloud environments.展开更多
基金This work is supported by the National High Technology Research and Development Program ofChina(2 0 0 2 AA135 2 30 ) and the Major Project of National Natural Science Foundation of Beijing(4 0 110 0 2 ) .
文摘The problem of long transactions is a significant problem in spatial database. The checkout mechanism and multi version mechanism are two kind methods of solving the problem of long transactions. In this paper, we present a Shallow Version Management mechanism to realize multi version mechanism in spatial database. And we introduced a increment storage and dynamic version views building method to improve efficiency of storing and consulting. We also illuminate how to resolve the problem of long transaction concurrency control in spatial database by using multi version mechanism. At the end of this paper, we introduce some required means to version management in spatial database, like converge, compress and delete.
基金This research is supported by National Natural Science Foundation of China
文摘The data model of WHYMX complicates transaction management. Traditional locking method is not powerful enough to solve the new problem of concurrency control of WHYMX's transaction. This paper presents a number of concurrency control algorithms based on the extended locking method.
文摘This paper presents a practical concurrency control mechanism - ObjectLockingin OODBMS. Object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classes. Bythe properties of parallelity and coatativity between high level operations,proper lock modes for each operation are desigued and the compatibility matrixis constructed. With these lock modes, phatoms are kept away from databasesand a high degree of concurrency is achieved.
文摘Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real time databases in most cases. On the other hand, relaxed serializability including epsilon serializability and similarity serializability can allow more real time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real time databases can be greatly improved.
文摘An integrated method for concurrency control in parallel real-time databases has been proposed in this paper. The nested transaction model has been investigated to offer more atomic execution units and finer grained control within in a transaction. Based on the classical nested locking protocol and the speculative concurrency control approach, a two-shadow adaptive concurrency control protocol, which combines the Sacrifice based Optimistic Concurrency Control (OPT-Sacrifice) and High Priority two-phase locking (HP2PL) algorithms together to support both optimistic and pessimistic shadow of each sub-transaction, has been proposed to increase the likelihood of successful timely commitment and to avoid unnecessary replication overload.
文摘This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are proposed in the paper. The ideas of single queue scheduling(SQS) and dual queue scheduling (DQS) are proposed and the algorithm and the performance evaluation for these two scheduling are presented in some paper. This paper describes a new idea of thescheduling for MGL, compatible requests first (CRF). Combining the new idea with SQS and DQS,we propose two new scheduling algorithms called CRFS and CRFD. After describing the simulationmodel, this paper illustrates the comparisons of the performance among these four algorithms. Asshown in the experiments, DQS has better performance than SQS, CRFD is better than DQS, CRFSperforms better than SQS, and CRFS is the best one of these four scheduling algorithms.
文摘In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.
文摘This paper covers the transaction management of C-POREL, i. e. the distributed rela-tional data base management system on a microcomputer network. Presented in the pa-per are the concurrency control strategy of transactions in C-POREL, the mechanism ofthe local and global recovery, the reliable state control protocol RSC for getting the ro-bustness of the network and the protocol for processing distributed multisite transactions,and the outline of the architecture of the transaction manager TM of C-POREL.
文摘We have considered a method called Enhanced Rollback Migration Protocol, which potentially has the effects of compressing the period of compensations in a long-lived transaction, since before. In general, a compensation transaction can recover an irregular status of a long-lived transaction into the original status without holding unnecessary resources by making its consistency tentatively loose. However, it has also been pointed out that there is a difficulty of maintaining the isolation between a pair of transactions when executed in parallel. In particular, this could be more prominent under modernized scalable cloud environments. Thus, there is a proposal for concurrency control for the service level. However, there is still another risk that more computer resources will be consumed than actually necessary and an unnecessary stagnation of the processing will be caused if concurrency control is naively applied without careful consideration. Therefore, we need to implement a functionality which can optimize the processing of a long-lived transaction by selecting a suitable method between concurrency control and compensation transactions. In this paper, we propose a method in which optimistic concurrency control is applied for long-lived transactions. Furthermore, a pair of verification phases is carried out. At the beginning from a safe point, an attempt of verification is done. Then if the difficulty of isolation on a long-lived transaction executed under a competitive situation is estimated, concurrency control for the service level is applied. Alternatively, a long-lived transaction without any concurrency control is executed. At the next reachable safe point, another attempt of verification is performed. Then if a failure of serialization is detected, a set of compensation transactions is invoked to recover the original long-lived transaction by returning to the first safe point. We evaluated this approach by using numerical simulations and confirmed the basic features. This approach can realize optimizing and enhancing the performance of a long-lived transaction. We regard this approach applicable even to the modernized scalable cloud environments.
