VMS Help PASCAL, Predeclared Routines, Low Level, BARRIER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The BARRIER procedure causes a memory barrier instruction to  be
  emitted   to   synchronize   pending   memory   updates   in   a
  multi-processor environment.

  Syntax:

    BARRIER

  The BARRIER procedure has no parameters.