The following is relevant when working with documents spread over many files:
query-replaceon all files which are part of a multifile document.
TeX-masterfor AUCTeX or
tex-main-filefor the standard Emacs LaTeX mode) containing the name of the master file. For example, to set the file variable
TeX-master, include something like the following at the end of each TeX file:
%%% Local Variables: *** %%% mode:latex *** %%% TeX-master: "thesis.tex" *** %%% End: ***
AUCTeX with the setting
(setq-default TeX-master nil)
will actually ask you for each new file about the master file and insert this comment automatically. For more details see the documentation of the AUCTeX (see Multifile), the documentation about the Emacs (La)TeX mode (see TeX Print) and the Emacs documentation on File Variables (see File Variables).