A database system includes a locking mechanism for a view defined on one or more base relations. A B-tree index is defined on the view. In response to updates of a base relation, predefined locks are placed on the view. With locking mechanisms according to some embodiments of the invention, concurrency of transactions that access the view and B-tree index is enhanced by enabling concurrent updates of the materialized view by plural transactions in certain cases, while avoiding read-write and write-read conflicts.