Would it be beneficial to have a dedicated service running the process engine or is this an over kill? When should we consider adding it? How many processes can be completed with the engine verses a Background (BG) service?
We have many customers running a dedicated BG service for the Job Scheduler and a dedicated BG service for the Process Engine. You would not want to use an Application (APP) service to run either.
Usually the "when to dedicate" has to do with running into memory constraints or other system resource constraints.
An added benefit of having a dedicated service running the Process Engine and a dedicated service running the Job Scheduler is that you can stop and start them independently.
The "When to add a second Process Engine" occurs when 1 Process Engine can't keep up with the requests. You can monitor the application as an administrator user by navigating to Administration, Process Engines page. You'll need to have the process engine monitoring global security access right.
It's tough to give an exact number of how many can be processed, because there are many factors including process/step complexity and system resources. If you're concerned that there is a bottle neck the monitoring page is a good place to look. A good guide line is that the maximum a single process engine can handle efficiently is about 3500 processes. When customers start consistently seeing 3000+ processes on each of their process engines, it is probably time to consider adding a new one to allow for growth. However, bottlenecks can happen sooner for some customers who have very complex processes/steps.
Also please make sure you have sufficient memory available on the server before adding a bg. For example if you have only 4gb total on the server and it is already running CSA, APP, BG, and beacon; adding another BG would really push the limits of the available memory.
You can add a second BG service in the CSA on the services tab. Once it's added you can access the Background service Properties. Here you can check or uncheck the "Run Process Engine" or "Run Job Scheduler" check boxes appropriately. You'll need to restart the Service for the settings to take affect.