Abstract: The present invention provides a method and apparatus for concurrency control in an object oriented database management system having a plurality of users accessing the system at the same time, and allowing editing of the database while other users are concurrently searching the database. The present invention may be advantageously used in a client/server architecture comprising a knowledge base client and a knowledge base server. In a preferred embodiment, the knowledge base server may include an object oriented lock manager, a dynamic class manager, a connection manager, a query manager, a handle manager, a units manager, a database manager, and a file manager. The concurrency control mechanism includes a lock holder table. The present invention provides a method and apparatus for providing concurrency control in an object oriented database managemant system using only three types of lock modes: a class share lock, a tree update lock, and a tree exclusive lock.