Nowadays, the application area of database systems grows wide rapidly and requires higher performance in transaction processing systems. Guaranteeing high performance of transaction processing system on the top of general purpose operating system has many advantages like high portability, easy migration of applications, and easy application development. We designed and implemented a parallel transaction processing system on the top of general purpose operating system which utilize not only inter but also intra transaction parallelism in order to obtain high performance. The prototype of our transaction processing system MUSE was implemented in the multiprocessor computer on the top of UNIX operating system. MUSE consists of 6 modules and is based on N:M client server process model. To support parallel execution of transactions, PARBEGIN and PAREND are provided. The run-time characteristics revealed that the granule of the critical region plays an important role in getting high performance.