How to search whole buffer?

[Ulrich Scholz <d7@thispla.net>]

Hi, I'm using search-forward to search and replace strings.

(defun my-replace nil "change escape sequences to umlauts"
  (interactive)
   (while (search-forward "<DF>" nil t)
           (replace-match "ß" nil nil))
)

But that search does not search the whole buffer.  In particular, if I
perform two subsequent searches then the second does not find
anything.  So either I'm looking for something like
search-buffer (which I did not find yet) or for a method to set the
begin of the search to the first character of the current buffer.
(I've had a look at search but there was no documentation)

Thanks,

Ulrich