Timestamp–based algorithms have been proposed to protect distributed database from inconsistencies during concurrent access. In such algorithms, transactions may reach a paricular site out of the order of their timestamps, due to unexpected network delays. This causes conflicts which the distributed concurrency control mechanism has to cope with. In this paper we analyze the essential features ...

This work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. Locking and timestamping are two popular approaches to concurrency control in database systems. Timestamp-based algorithms have been proposed to protect distributed databases from inconsistencies during concurrent access. In these algorithm...

The multidatabase systems(MDBSs) are an integration of local database systems into a global distributed database system. The objectives of global transaction management are to avoid the inconsistent retrievals and to guarantee the global serializability under the existence of indirect conflict which is unknown to the global transaction manager(GTM). Many researches have shown that it is difficu...

A family of optimistic concurrency control protocols for real-time persistent systems with critical performance requirements and very tight deadlines is proposed. Under assumptions that almost all transactions are extremely short and read-only and the entire database resides in main memory (which are realistic for this type of applications), we propose distributed concurrency control protocols ...

We consider categories of coalgebras as (co)-fibred over a base category of parameters and analyse categorical constructions in the total category of deterministic and non-deterministic coalgebras.

The global inter-site constraints is to describe the integrity constraints associated with data items in diierent local databases, which specify the global connguration of the data that are considered semantically correct. Locally consistent transactions may generate global inconsistencies with the existence of global integrity constraints. Hence, we need the global transaction manager that ens...