The EXPORTALL option controls whether to export all externally defined procedures and variable so that a DLL application can use them.
.-EXPORTALL---. >>-+-NOEXPORTALL-+---------------------------------------------><
Under EXPORTALL, all externally defined procedures and variables are exported except those that specify OPTION(DLLINTERNAL).
Under NOEXPORTALL, no externally defined procedures and variables are exported except those that specify OPTION(DLLEXTERNAL) or OPTIONS(FETCHABLE).
When linking a module as a DLL that will be simply fetched (rather than accessed through DLL functions), you must use the NOEXPORTALL option.
The default is EXPORTALL, but NOEXPORTALL is better for performance.