@Hans Feldmann The individual processors allow for concurrent task changes. By default they all have one concurrent task. For each additional concurrent task, you are giving that processor the opportunity to request an additional thread from the NiFi controller to do work in parallel. (Think of it as two copies of the same processor doing working different files or batches of files). If there isn't sufficient files in the incoming queue then any additional concurrent tasks are not utilized. The flip side is if you allocate two many concurrent tasks to a single processor, that processor may itself end up using two many threads from the NiFi controller's resource pull resulting in a thread starvation to other processors. So star with the default and setup by one increment at a time in place of backlog in your flow. The NiFi controller also has a setting that limits the maximum number of threads it can use from the underlying hardware. This is the other thing Andrew was mentioning. A restart of NiFi is NOT needed when you make changes to these values. The defaults are low (10 timer driven and 5 event driven). I would set the timer driven to no more then double the number of cores your hardware has. Thanks, Matt ... View more