We propose an advanced transaction scheduling protocol to improve the degree of concurrency and to satisfy security requirements for a multilevel secure database in a wireless mobile network environment. Wireless communication is characterized by frequent spurious disconnections. So a short-lived transaction must quickly access the database without any delay by a long-lived one. We adapted a two-phase locking protocol to the multilevel secure database. Altruistic locking, as an advanced protocol, has attempted to reduce the delay effect associated with the lock release moment, by use of the idea of donation. An improved form of altruism has also been deployed for extended altruistic locking (XAL). This is in a way that the scope for data to be released early is enlarged even to include data that was not initially intended to be donated. Our protocol is based on extended altruistic locking, but a new method, namely two-way donation locking for multilevel secure database (2DL/MLS), is additionally used in order to satisfy security requirements and concurrency. The efficiency of the proposed protocol was verified by experimental results.
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