Cluster locking or container locking for concurrency control is illustrated in the figure below. In this form of locking, all data clustered together (on a page or multiple pages) will be locked simultaneously. This applies only to clusters of objects in ODBMSs. Note that in this example, the cluster of objects spans portions of three pages.
Additional information on this subject along with examples of multi-user considerations can be found in the Object Database Handbook.
More on the general topic: Concurrency Control and Locking