Why job is running for long period of time?

1. It could be an issue with CPU processors and memory was consumed highly that no sufficient memory available to process further.
2. Check for the ST06 transaction for CPU utilization and Memory consumption
3. Check for the Lock entry list in ST12 transaction whether any lock has been held by any user for long period of time.
4. It might also be connected with the program that the job is running. If the program is running for the 1st time then it might take time to process and complete