/sys$common/syshlp/helplib.hlb MERGE, /STABLE, Example  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  $ SORT/KEY=(POS:1,SIZ:5,DECIMAL)/STABLE PRICESA.DAT,PRICESB.DAT, -
  _$ PRICESC.DAT SUMMARY.LIS

      In this sort operation, records with equal keys from
      PRICESA.DAT will be listed first, followed by those from
      PRICESB.DAT, followed by those from PRICESC.DAT.