ASH is also configurable. Depending on your Oracle release, there are around a dozen hidden ASH-related instance parameters. One in particular, _ash_sampling_inteval, controls how often ASH samples. The default is set to once each second, but this can be changed to increase statistical accuracy or to decrease collection impact.

I think you'll agree that ASH is quite a technical achievement and can be very useful during performance firefighting.

Before I delve into ASH internals, I will demonstrate a few ASH-based reports to give you a taste of what you can do with ASH. While OraPub's OSM tool kit contains around a dozen ASH scripts, I will demonstrate only a few. The underlying SQL is very simple and you can download the scripts for free and analyze them. Just keep in mind that what you'll see here is just a fraction of what you can do with ASH. My intention is to show you ASH's flexibility, ease of use, and spot-on ORTA diagnostic power.