Semipermeable transactions and semantics-based concurrency control for multidatabases

The problem of concurrency control for transactions in a multidatabase system has received considerable attention. Many of the proposed solutions offer either small increases in concurrency compared to sequential execution, or make unrealistic assumptions about the operating environment. The authors approach the problem by combining existing solutions which guarantee global serializability and then use the semantics of global transactions to significantly increase the degree of concurrency. The idea is to specify acceptable violations of global serializability when allowed by the semantics of global transactions. This is accomplished by allowing global transactions to interleave globally based on the permeability of the transactions