Exploring Consistency of Read-Only Transactions in Real-Time Systems

In this paper, we describe our current work on exploring the consistency of read-only transactions (ROT) in real-time systems. A ROT is a transaction that only reads, but does not update any data items. Since there is a significant proportion of ROTs in several real-time systems, it is important to investigate how to process ROTs efficiently with separate algorithms. We identify three different consistency requirements for ROTs. Particularly, we define a weaker form of consistency, view consistency, which allows ROTs to perceive different serialization order of update transactions, thus permitting non-serializable execution of transactions. However, ROTs are still ensured to see consistent data. Based on view consistency, we present two algorithms which let ROTs read the most recent and consistent data without interfering with update transactions. The recency of data read by a ROT could be important in some real-time applications.