To ensure various degrees of data consistency and currency for read-only transactions, various new isolation levels are proposed in . Efficient implementation of these isolation levels is also proposed. This is used in a hybrid data transmission environment. The newly proposed consistency levels are independent of the existing concurrency protocols.
Although serializability is standard criteria for transaction processing in both stationary and mobile computing, it is, in itself, not sufficient for preventing read-only transactions from experiencing anomalies related to data currency. A start-time multiversion serialization graph (ST-MVSG) is a directed graph with nodes = commit (MVH) and edges E such that there is an edge representing every arbitrary dependency. Let MVH be a multiversion history over a set of committed transactions. Then MVH is BOT serializable if ST-MVSG is acyclic. In an MVH that contains a set of read-write transactions such that all read-write transactions are serializable, each read-only transaction satisfying READ-RULE is also serializable. This leads to the conclusion that MVH is strict forward BOT serializable if SFR-MVSG is serializ-able. In a multiversion history containing a set of read-write transactions such that all read-write transactions are serializable, each read-only transaction is serializable with respect to transactions belonging to the corresponding update. Simulation results demonstrate that this improves the throughput control and number of abort associated in transactions.
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