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

  ERROR - A constant  channel  expression  is  greater  than  99,  or  a
  variable  channel  expression  is  greater  than  119.  If the channel
  expression is a constant, change it to be less than or equal to 99.  A
  variable channel expression can be less than or equal to 119; however,
  channels in the range 100 to 119, inclusive are reserved for  programs
  using LIB$GET_LUN.