Tags are loaded as and when they are needed as PTC ALD works through a document. If you want to check for linked tags that are not used in your document you must ensure that PTC ALD has made all possible calls for the tag first. Because rasters are not loaded until they are needed for display, the safest way of doing this would be to print the document (to screen or a file), then reformat the document with a tformat operation and then use ttlchk. You could then assume that linked tags which still had not been loaded were not being used any more (although some could still be required for further work on the document, for example control streams that you had not used on this occasion, text streams that you had not displayed, etc.)