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

  Controls whether the compiler produces diagnostic messages when
  variables or arrays (created in COMMON or EQUIVALENCE statements)
  are declared in such a way that they cross natural boundaries for
  their data size.  For example, a diagnostic message is issued if
  /WARNINGS=ALIGNMENT is in effect and the virtual address of a
  REAL*8 variable is not a multiple of 8.

  The default is /WARNINGS=NOALIGNMENT.

  It is recommended that you specify /WARNINGS=ALIGNMENT if data in
  COMMON blocks (or which appears in EQUIVALENCE declarations) is to
  be used in a vectorized program.

  Eliminating unaligned data can improve performance on VAX and is
  very important for applications being migrated to the Alpha
  architecture.

  Alignment warnings for specific STRUCTURE and COMMON declarations can
  be controlled using the /WARNINGS=ALIGNMENT qualifier on the
  CDEC$ OPTIONS directive.