Weak consistency of read-only transactions: A tool to improve concurrency in heterogeneous locking protocols

  • R. C. Hansdah
  • L. M. Patnaik
Session 5 Database Theory
Part of the Lecture Notes in Computer Science book series (LNCS, volume 287)


Three different types of consistencies, viz., semiweak, weak, and strong, of a read-only transaction in a schedule s of a set T of transactions are defined and these are compared with the existing notions of consistencies of a read-only transaction in a schedule. We present a technique that enables a user to control the consistency of a read-only transaction in heterogeneous locking protocols. Since the weak consistency of a read-only transaction improves concurrency in heterogeneous locking protocols, the users can help to improve concurrency in heterogeneous locking protocols by supplying the consistency requirements of read-only transactions. A heterogeneous locking protocol P' derived from a locking protocol P that uses exclusive mode locks only and ensures serializability need not be deadlock-free. We present a sufficient condition that ensures the deadlock-freeness of P′, when P is deadlock-free and all the read-only transactions in P′ are two phase.


Data Item Database Management System Strong Consistency Partial Schedule Weak Consistency 
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Copyright information

© Springer-Verlag Berlin Heidelberg 1987

Authors and Affiliations

  • R. C. Hansdah
    • 1
  • L. M. Patnaik
    • 1
  1. 1.Department of Computer Science and AutomationIndian Institute of ScienceBangaloreIndia

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