Delay debug mode for C requires the FUNCEVENT(ENTRYCALL) compiler suboption

You must specify the FUNCEVENT(ENTRYCALL) compiler option when you compile your programs for delay debug usage.

Usage notes:

The FUNCEVENT(ENTRYCALL) compiler option is available in the z/OS 2.1 XL C/C++ compiler with the PTF for APAR PI19326 applied.
If your C application runs on UNIX System Services with imported functions from a DLL module and you want to delay the starting of a debug session until one of those functions is called, the DLL module name must be the same as the load library name.