Oracle Streaming defines TRIM_HORIZON as the cursor type that starts consumption from theoldest available message in the stream. Because Streaming retains messages only for the configured retention period, “oldest available” means the earliest record that has not yet aged out of retention. Oracle specifically recommends creating a cursor at TRIM_HORIZON when a consumer needs to process all currently retained messages. LATEST starts with messages published after the cursor is created. AT_TIME begins at or after a specified timestamp, while AFTER_OFFSET begins after an explicitly supplied partition offset. Consequently, none of those alternatives guarantees starting from the earliest retained record. TRIM_HORIZON is therefore the correct cursor for replaying the complete message history that remains available in the stream.