Prior to Ingres II 2.5, the Ingres DBMS would hold a page lock on the leaf pages on B-tree tables for a serializable update transaction, even when using row locking. This was done to prevent other users from inserting a row in the qualified range to be updated. In Ingres II 2.5, the DBMS uses a value locking protocol for serializable transactions with an equal predicate, thereby allowing better concurrency.