10 Software vendors who rely on good performance data hate ASH with a passion. Third-party performance vendors spend a considerable amount of time and money creating and maintaining their low-overhead data collection facility. They would welcome ASH, except Oracle forces their customers to license ASH, which also allows customer to use Oracle performance products. So now the customer must ask the question, "Why purchase both Oracle's performance products and this vendor's product?" This is a question performance product vendors want to avoid.

11 Obviously, building a tool to sample v$session can be done. But on a large Oracle system, directly sampling from v$session and then storing that information can easily take over a minute!

12 Now don't panic. Every time I have checked, my inferences and ASH data match perfectly. We just need to be a little more careful and understand what we are viewing.