Explicitly defining a cursor as read-only can improve performance by avoiding table locking. This allows other SQL requests to execute in parallel. Therefore when a cursor will only be used to read data, without modifying anything, the ``++FOR READ ONLY++`` clause or its synonyn, ``++FOR FETCH ONLY++``, should be used.
Conversely when a cursor will modify data, that too should be specified using the ``++FOR UPDATE++`` clause.
In short, it's better to always explicitly define the purpose of the cursor with help of the ``++FOR READ ONLY++``, ``++FOR FETCH ONLY++`` or ``++FOR UPDATE++`` clauses.