Specifies that the cursor is used to update the database.

    Use an update-only cursor when you plan to update most of the
    rows you are fetching. The update-only cursor causes Oracle
    Rdb to apply more restrictive locking during the initial read
    operation, so that locks do not need to be upgraded later from
    READ to exclusive WRITE. This reduces the total number of lock
    requests per query, and may help to avoid deadlocks.

    Use update-only table cursors to modify table rows. SQL does not
    allow update-only list cursors.