Library /sys$common/syshlp/basichelp.hlb Run time errors, ARRMUSSQU  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Arrays must be square (ERR=239)

  The program attempts matrix inversion (MAT INV) on an  array  that  is
  not  square.  Redimension the array to be square before performing MAT
  INV.