/sys$common/syshlp/helplib.hlb PASCAL, Attributes, KEY, Options, CHANGES  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  This option allows you to specify that changes can be  performed
  on the key.

  The default for the primary key is NOCHANGES and the default for
  alternate  keys  is  CHANGES.   You  can override the CHANGES on
  alternate keys with NOCHANGES.  It is illegal to specify CHANGES
  on the primary key.

  When opening an  existing  file,  the  Pascal  Run-Time  Library
  ignores this option.