A Suggestion for a New Reliable Real-Time Nested Transaction Model

Focusing on a simpler problem of scheduling nested transactions for a single processor, we present real time nested transaction model. A concept of nested transactions proposed by Moss is needed to provide flexibility and performance in distributed complex and dynamic systems since real-time systems become complex and distributed. Moss's model is extended to hard real-time systems by the addition of explicit timing constraints. Though the model allows multiprocessor and distributed implementations, solving a real-time nested transaction model scheduling problem for a single processor is viewed first step toward solving the more general problem. For a single-processor environment, the well-known Priority Ceiling Protocol can be extended to support a reliable nested transaction model, yielding an integrated concurrency control and scheduling algorithm that guarantees timing constraints of a set of nested transactions and maintains consistency of the database. It can be verified that the Real-Time Nested Priority Ceiling Protocol prevents unbounded blocking and deadlock, and maintains the serializability of a set of hard real-time transactions.