locate-fcodes-file

locate-fcodes-file is a variable defined in `locate.el'.
Its value is

nil

Documentation:
File name for the database of file names used by `locate'.
If non-nil, `locate' uses this name in the header of the `*Locate*'
buffer. If nil, it mentions no file name in that header.

Just setting this variable does not actually change the database
that `locate' searches. The executive program that the Emacs
function `locate' uses, as given by the variables `locate-command'
or `locate-make-command-line', determines the database.

You can customize this variable.