A locator passes a LOB value reference from a client to the server application or user-defined function without passing the LOB value itself. Its purpose is to minimize message traffic, enhancing system performance in the process. Queries that request LOB data are serviced with intermediate results that contain locators to LOB data, not the LOB data itself.
When you use a locator as a parameter in a subsequent request, the result is exactly as if the associated LOB value had been used directly. Locators can be used in almost any context where a LOB value is valid.
Locators are instantiated in the result set of an SQL query and bound to an application program or UDF variable by an application-specific method.
Locators exist for a limited time within the session in which they are created. Their precise life span depends on the specific application.