Sometimes a process will hang indefinitely without finishing. This issue is usually followed by the error "Process is already running, executionId......". The platform will not allow the process to execute again until the first execution is finished. When a process gets stuck in a pending state it is essentially stopping the process from running at all and prevents any further executions of the process, which can be very troublesome in a Production environment, especially if the process is supposed to execute many times in a single day.
If you encounter this issue and find that you cannot manually terminate the process you should follow the steps in this link to terminate the process:
There are several reasons that this may occur, however one of the most common causes for this is low memory issues with your Atom. If your Atom's available memory is ALL being used the Atom will crash. If the Atoms available memory is close to being all used you can experience issues like a hung process. You will see Low Memory warnings in your Atoms container logs if you are approaching the memory threshold. You can view your Atoms container logs in Atom Management. Click on the Atoms name the select the Log Files tab and select Atom Logs and check the box Include Bin Logs. You must also choose the day that you want the logs for.
Once you confirm you are having Low Memory issues you will want to increase the Memory available to the Atom. You can view your Atom memory settings in Atom Management under the Startup Properties tab. Maximum RAM Available will show you how much memory you have allotted for your Atom. For a 32-bit Atom, the default is 512 MB and the highest recommended setting is 1024 MB. A 64-bit Atom is able to use more memory as long as it is available on the machine. A server usually needs 512 MB to 1 GB for the operating system; the rest of the memory can be allocated to the JVM. You can view the memory available on your machine on the same tab. It is labeled Total System Memory.
Here is an article that explains how to increase the the available memory for your Atom.