With the rapid progress in wireless communications, mobile devices are likely to form a new computing platform in the next few years. More and more complex data management operations are expected to be executed in such mobile devices. Current transaction processing techniques do not apply to the area very well. They provide very limited flexibility and performance, and they cannot respond and adapt to the changes very well. In this paper, we propose a QoS-aware transaction processing framework which gracefully adapts to the changes in mobile devices, provides great flexibility to the transaction service and improves performance. The work is done in the context of an ongoing research project called SyD, System on Mobile Devices.