October 3, 2006 Abstract: The Object Oriented Database Management System (OODBMS) has been in existence now for nearly 2 decades. The major vendors conceived and began implementing them in the late 80’s accommodating OO languages like Smalltalk, C++ and Java, with commercial products shipping in the mid 90’s. In the beginning, there was a great expectation that the OODBMS would replace the RDBMS as the database of choice for future applications. The “great expectation” has not come to fruition and it is an assertion in this paper that ONE of the major reasons for this comes down to OODBMS architecture. That is, the OODBMS architecture and it’s impact on the expectations of early adopters. Many successfully deployed applications have demonstrated that choosing the right OODBMS architecture allows the building of high performance, highly concurrent and scalable solutions. This paper seeks to examine the issue of expectation along with examining the differences between the 3 most common commercial OODB architectures.