A switching system generally uses its own real-time operating system and DBMS. One of the important issues for providing a test environment on a host computer is to prepare a DBMS simulator, which has the same functionality as the DBMS in the target switching system and can run on a general-purpose computer. It is difficult to guarantee that both the DBMS and the simulator will have the same functions and behaviors.Therefore, we propose a host DBMS, H-DREAMS (Distributed and Real-time DBMS for Host computer), which can be automatically generated from the source system of the target DBMS and can run on the host computer to test a program. The source programs of the target DBMS are fully reusable in making the host DBMS. H-DREAMS acts like the target DBMS and can support real-time characteristics using a relative timer mechanism in the run-time system. It makes switching software portable and part of the functional blocks of the switching software can be moved to other general-purpose computers.