Locking

Locking in the database typically occurs when a record is modified, deleted or inserted. The lock persists until the transaction that the modification is part of is committed or aborted. This type of locking can be referred to as implicit locking, because the lock is taken implicitly by virtue of the database being modified. Records can also be locked explicitly by simply selecting them in a mode that causes the records to be locked even though they have not been modified. Locking allows the database server to serialize changes to the content of the object being locked to prevent corruption of data. Explicit locking allows the application to obtain exclusive control over data.