-O, -qoptimize

Open XL C/C++ for z/OS® supports the -O0, -O1, -O2, and -O3 optimization levels. The -O4 and -O5 optimization levels that are supported by z/OS XL C/C++ are not available in Open XL C/C++ for z/OS.

The optimization level of -O is equivalent to -O2 in z/OS XL C/C++, but it is equivalent to -O1 in Open XL C/C++ for z/OS.

In z/OS XL C/C++, the -qoptimize option specifies whether to optimize code during compilation and, if so, at which level. If you were using -qoptimize in z/OS XL C/C++, use --optimize=<level>, -O0, -O1, -O2, -O3, or -Ofast in Open XL C/C++ for z/OS to achieve the similar effect.