You must not declare as EXTERNAL a variable whose name, unless it is the name of an IBM provided function such as PLIXOPT or PLITDLI, begins with any of the following:
The code generator for the new compiler uses C functions to perform some tasks, particularly under OPT(0). As a result, unless you are intending to invoke the C function directly, you must not declare as EXTERNAL a variable with any of the following names:
The PLIXHD variable is no longer used as the heading in storage reports. Consequently, the identifier PLIXHD is no longer reserved, and you can declare it and use it as you would declare and use any other variable (as long as you don't declare it EXTERNAL).