Patent ID: 6944615

Claim:
A database management system (DBMS) for managing a database application, the database application including a database having at least one table, and an index having at least one unique key index table corresponding to the at least one table, the DBMS comprising: a data manager for managing updates of the database; an index manager for managing updates of the unique key table index; a transaction manager for executing database transactions in cooperation with the data manager and the index manager; and, a lock manager cooperative with the index manager and the data manager for restricting access to a first table element of said at least one table by assigning one or more locks thereto, said locks being selected from a plurality of lock types including at least, an exclusive X-lock that enables exclusive access to the first table element, the exclusive X-lock including a Delete X-lock attribute logically associated therewith, a SET state of the Delete X-lock attribute being indicative of a transaction holding the X-lock being a delete transaction; an unconditional S-lock that enables shared access to the first table element and is selectively assigned by the lock manager to the first table element only when the first table element is without an exclusive X-lock previously assigned thereto; and a conditional S-lock that enables shared access to the first table element and is selectively assigned by the lock manager to the first table element only when the first table element is either without an exclusive X-lock previously assigned thereto or is without an exclusive X-lock having its Delete X-lock attribute SET assigned thereto.