When the news forum is created, the name of the forum is "News forum" (depending of the language, of course).
Even if you rename "News forum" in the forum.php file, the existing news forums keep their name "News forum".
So, you have to execute the request :
UPDATE forum SET name = "NEW_NAME" WHERE type = 'news' and name = 'News forum"
But I discovered that it is not enough ! You have to rebuild the cache course as well ! The forum name is also in the field modinfo of the course table. This field is used as cache. Even if you execute the previous request, when you visit a course, the old name still displays.
To display the new name, the cache course must be rebuilt. If you edit the forum, the new name will appears in the name field and when you saved the page, the cache course is rebuilt.
More information here :
- modinfo in the course table (2005)
- a problem with modinfo field in mdl_course database table (2008)
- courses and modinfo (2007)
I think that the best is to call the function rebuild_course_cache($courseid), where $courseid is the id field of the course.