DB2 CLI can run a subset of functions asynchronously; the DB2 CLI driver returns control to the application after calling the function, but before that function has finished executing. The function returns SQL_STILL_EXECUTING each time it is called until it is finished running, at which point it returns a different value (SQL_SUCCESS for example).
Asynchronous execution is only beneficial on single-threaded operating systems. Applications that run on multithreaded operating systems should execute functions on separate threads instead.
Asynchronous execution is possible for those functions that normally send a request to the server and then wait for a response. Rather than waiting, a function executing asynchronously returns control to the application. The application can then perform other tasks, or return control to the operating system, and use an interrupt to repeatedly poll the function until a return code other than SQL_STILL_EXECUTING is returned.