To understand the workload for your given system you will need to gather information on the following main points:
Who is doing the work? - Which users are running workloads, which applications are running workloads?
What types of work are done on the system? - Are these workloads batch, ad-hoc, resource intensive (which resources) and are these mixed or separated in some form?
When are certain types being done? - Are there different workloads during different times of the day, are there different priorities during different time windows?
Where are performance problem areas? - Are there any specific issues in today's workload, why are these problems there, what is being done to fix these?
What are the priorities, and do they change during a time window? - Which of the various workloads are most important and when?
Are there priority conflicts? - And if so, who is going to make sure the right decisions are made on the real priorities?