Distributed transaction monitor is the fundamental software for critical transactional applications across network. We concern its quality from the point of view of practicality. This paper presents the key technologies during the reconstruction of the distributed transaction monitor OnceTX1.0 to OnceTX2.0, including scalable architecture, multi-phase concurrency control, dynamic configuration and access for system services, and optimization of message organization and processing. OnceTX2.0 is now applicable to not only small-scale and tight-coupling transaction applications, but also geographically dispersed applications with transaction demands. Its performance has also been enhanced, which is proved by the benchmark results. Moreover, extensibility and maintainability are achieved.