When Explicit Locking Is Necessary
The system automatically places locks on database objects each time an SQL request is performed. Therefore, the use of the LOCKING modifier is seldom necessary. Explicit user‑specified locks are only useful when you need to override the automatic locking specified by the Optimizer and placed by the Lock Manager. Overriding the default may be necessary to prevent deadlock if subsequent requests in the transaction require a higher level lock for an object.