A transaction model for mobile computing

We introduce a prewrite operation before a write operation in a mobile transaction to improve data availability. A prewrite operation does not update the state of a data object but only makes visible the value that the data object will have after the commit of the transaction. Once the transaction has read all the values and declares all the prewrites, it can precommit at a mobile host. The remaining transaction's execution is shifted to the stationary host. Writes on a database consume both time and resources at the stationary host and are therefore delayed. A pre-committed transaction's prewrite values are made visible both at mobile and stationary hosts before the final commit of the transaction. This increases data availability during frequent disconnection common in mobile computing. Since the expensive part of the transaction execution is shifted to the stationary host, it reduces the computing expenses at the mobile host.