This SVC is used only by an interactive debugger working with z/OS® UNIX PTRACE functions. When the SVC is run, it causes the z/OS UNIX PTRACE SVC routine to get control. The SVC routine communicates back to the debugger to notify it that a breakpoint has been reached. After the debugging is complete, control returns to the program. For more information, refer to the description of BPX1PTR in z/OS UNIX System Services Programming: Assembler Callable Services Reference.