When several transactions execute concurrently in a database, the isolation property may no longer be preserved. It is necessary for the system to control the interaction among the concurrent transactions. This paper presents a new locking model for concurrency control in object oriented database systems. This model is motivated by a desire to provide high concurrency and low locking overheads in accessing objects. The proposed model consists of a rich set of lock modes, hash table, lock-based signatures and B+ trees. The performance study result shows that the proposed model performs well for all possible operations on objects.