If the sample can be assigned to a certain chemical context (like "cement", "mineral" or "organic" compound), it is recommended to use this information to restrict the search-match to corresponding subfiles of the COD or PDF. You can do so on the "Subfiles" page of the Restraints tab.
The basic advantage of this limitation is the reduction of the number of candidate entries in the candidate list which makes the calculations (especially PFSM) faster and the final selection of the matching entries by the user a lot easier.
By default, entries of all subfiles are accepted. You can change this simply by marking the checkboxes of the subfiles you would like to accept. If you would like to select only a few or nearly all subfiles, you can use the Clear All or the Select All buttons at the bottom of the tabsheet.