Concurrency control and recovery in database systems
Concurrency control and recovery in database systems
Scheduling real-time transactions: a performance evaluation
ACM Transactions on Database Systems (TODS)
Data access scheduling in firm real-time database systems
Real-Time Systems - Special issue: real-time databases
Fundamentals of database systems (2nd ed.)
Fundamentals of database systems (2nd ed.)
A token-based synchronization scheme for distributed real-time databases
Information Systems
Read-only transactions in a distributed database
ACM Transactions on Database Systems (TODS)
Object-Based Semantic Real-Time Concurrency Control with Bounded Imprecision
IEEE Transactions on Knowledge and Data Engineering
A Priority Ceiling Protocol with Dynamic Adjustment of Serialization Order
ICDE '97 Proceedings of the Thirteenth International Conference on Data Engineering
Divergence Control for Epsilon-Serializability
Proceedings of the Eighth International Conference on Data Engineering
Scheduling Real-time Transactions: a Performance Evaluation
VLDB '88 Proceedings of the 14th International Conference on Very Large Data Bases
Experimental Evaluation of Real-Time Optimistic Concurrency Control Schemes
VLDB '91 Proceedings of the 17th International Conference on Very Large Data Bases
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In this paper, we investigate the approach to relaxing consistency requirement of serializability to improve the performance of real-time database systems. We make use of the property that a read-only transaction (ROT) only reads, but does not update any data item. Since there is a significant proportion of ROTs in several real-time systems, it is important to investigate how to process ROTs effectively. We define a weaker form of consistency, view consistency, which allows ROTs to perceive different serialization orders of update transactions. Although view consistency permits non-serializablility, ROTs are still ensured to see consistent data. We devise a separate algorithm to process ROTs from update transactions for view consistency. For comparison, we devise another separate algorithm to process ROTs for strong consistency that is equivalent to serializability. Our simulation results show that the two separate algorithms outperform the locking and optimistic protocols significantly. Using separate algorithms reduces the interference between ROTs and update transactions. This reduced interference alleviates the impact of concurrency control on real-time priority-driven scheduling and improves the timeliness of the system. To our great surprise, the two separate algorithms perform almost the same. In our investigation, we found that most data conflicts between an ROT and update transactions are independent data conflicts. These independent data conflicts can be easily resolved by using a separate algorithm even under serializability. Thus, this observation indicates that using a separate algorithm to process ROTs from update transactions is more effective than relaxing consistency requirement.