Jacky,
Multithread safety means that if a sequence file is called by different threads, each sequence will have its own memory space. Therefore, if a sequence file that is being called by different threads contains local variables, the local variables of each sequence call will be allocated in different parts of the stack.
This functionality enables TestStand to run both the parallel and batch process models where the same test might be performed on different UUTs at the same time.
Regards,
Santiago D
