The TDFHOOK startup intercept allows starting an application under TDF control. Special intercept commands allow targeting subtasks within a started system. No TDF functionality requires any program modification to the source.

SVC screening of ATTACH, LOAD, LINK and XCTL, allow target tasks to be debugged within a multi-tasking address space. SVC screening of SPIE, ESPIE, STAE and ESTAE provide automatic system breakpoints for RTM exit creation, deletion, invocation and return within a targeted task.

PC screening, allows intercepting PC defined RTM exits (ESTAEX) and SRB scheduling (IEAMSCHD) in targeted subtasks. For ESTAEX, TDF inserts system breakpoints after the creation, cancellation, invocation and return within a targeted task. For IEAMSCHD, TDF inserts system breakpoints before and after the PC call and before and after the SRB execution. The scheduled SRB can be debugged as easily as a task.

Branch entry intercept breakpoints allow setting a breakpoint in select branch entry call, such as SETFRR, to intercept branch entry calls. For SETFRR, TDF sets system breakpoints after the add, replace, delete or purge function calls and before the FRR exit is called and after it returns.

Inheritance allows trapping attaches of target programs without trapping the attaching task. Pass-through allows trapping shared code even though one or more tasks using the shared code is not being debugged.