Locators are small data structures that contain information for accessing actual data of large objects (LOBs).
Locators are directly stored in database tables, while data can be stored in database tables or separately. Separate tablespaces are usually used for LOBs.
OceanBase Connector/J can perform the UPDATE, TRUNCATE, and READ operations on a LOB after it obtains the locator of the LOB. You can enable or disable LOB locators by configuring the database URL parameter supportLobLocator, which is true by default.
LOB prefetch
OceanBase Connector/J prefetches metadata of a LOB, such as its length, chunk size, start, and locator, during regular extraction operations to reduce the number of round trips. If a LOB column is selected for a result set, the server and OceanBase Connector/J support the prefetch of some or all data to the client when the locator is obtained. Then, subsequently read data is fetched from the prefetch buffer by API calls, without the need to make database round trips.