Using separate algorithms to process read-only transactions in real-time systems

In this paper, we investigate the approach of using separate algorithms to process read-only transactions in real-time systems. A read-only transaction (ROT) is a transaction that 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. Using an algorithm to process ROTs separately from update transactions may reduce 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. Moreover, we explore the different consistency requirements of ROTs. Particularly, we define a weaker form of consistency, view consistency, which allows ROTs to perceive different serialization order of update transactions. While view consistency permits non-serializability, ROTs are still ensured to see consistent data. We propose two robust algorithms for different consistency requirements of ROTs. The two algorithms are robust in the sense that they can be used in a compatible way so that a real-time system can provide different consistent data for different applications. The performance of two algorithms was examined through a series of simulation studies. The simulation results show that the two algorithms outperform the high-priority two-phase locking protocol.