The old_TRKSVR_CALL_SEARCH structure is unused but is included in this protocol because it affects the definition of the TRKSVR_MESSAGE_UNION, as defined in section 2.2.13.

 typedef struct {
   unsigned long cSearch;
   [size_is(cSearch)] old_TRK_FILE_TRACKING_INFORMATION* pSearches;
 } old_TRKSVR_CALL_SEARCH;