Here are two comparisons of OEM 10g's Performance Page before and after. Before there was only one performance page which was difficult to use for interpreting database performance. After my I joined OEM team in 2002 I redesign the page, creating two views of the performance page.
The first was for overall system peformance including throughput indicators, the primary graph was database load measured in AAS or average active sessions. The database load graph could be correlated with OS indicators such as CPU run queue size and memory paging. Ultimately only % CPU was used and memory paging was sadly left out due to real estate concerns of using two graphs (legitimate) and worries about overloading the data in the OS graph and having two different X axis units (debatable).
The second performance page I created (fondly called the "Kyle Page" in the OEM group since I had to fight long and hard for it although I actually had to fight just as long and hard if not more for the initial performance page). I like the "Kyle Page" better, from a DB point of view, because it shows a breakdown of where the load is coming from on the database from the perspective of Top SQL and Top Sessions. This second performance page is based solely on profiling data, known as ASH or Active Session History which allows the aggregation of data by different dimensions providing a much more powerful view into database performance.