RMS_PATH_TMO

   The RMS path cache in each process holds entries that translate
   DVI+DID+name to new DVI+DID. These are used to greatly speed
   up directory path walks. Cache entries representing ordinary
   directory lookups are invalidated through the volume directory
   sequence number mechanism (UDB$L_DIRSEQ), which is clocked
   on every volume dismount and each time a directory is deleted
   or renamed. However, there is no convenient mechanism for
   invalidating a cache entry that represents a symlink, whose
   interpretation is affected by logical names or modification of
   the symlink. The only way to eliminate stale cache entries is
   with a timeout. This parameter is the system-wide cache timeout.
   Special values:

         1 = don't keep cache entries
        -1 = keep cache entries forever
RMS_PATH_TMO is a DYNAMIC parameter.