1 research outputs found
A Concurrency Control Method Based on Commitment Ordering in Mobile Databases
Disconnection of mobile clients from server, in an unclear time and for an
unknown duration, due to mobility of mobile clients, is the most important
challenges for concurrency control in mobile database with client-server model.
Applying pessimistic common classic methods of concurrency control (like 2pl)
in mobile database leads to long duration blocking and increasing waiting time
of transactions. Because of high rate of aborting transactions, optimistic
methods aren`t appropriate in mobile database. In this article, OPCOT
concurrency control algorithm is introduced based on optimistic concurrency
control method. Reducing communications between mobile client and server,
decreasing blocking rate and deadlock of transactions, and increasing
concurrency degree are the most important motivation of using optimistic method
as the basis method of OPCOT algorithm. To reduce abortion rate of
transactions, in execution time of transactions` operators a timestamp is
assigned to them. In other to checking commitment ordering property of
scheduler, the assigned timestamp is used in server on time of commitment. In
this article, serializability of OPCOT algorithm scheduler has been proved by
using serializability graph. Results of evaluating simulation show that OPCOT
algorithm decreases abortion rate and waiting time of transactions in compare
to 2pl and optimistic algorithms.Comment: 15 pages, 13 figures, Journal: International Journal of Database
Management Systems (IJDMS