And here's a good one: In this screencast, Jon Haslam describes how on Oracle Solaris 11, DTrace is now integrated into Oracle Database V$ views to provide a top-to-bottom picture of a database transaction I/O -- from storage devices, through the Oracle Solaris kernel, up to Oracle Database 12c itself:
With this end-to-end view, you can easily identify I/O outliers -- transactions that are taking an unusually long time to complete -- and use this comprehensive data to identify and mitigate storage system problems that were previously extremely hard to debug.
This is a great demonstration of the power of DTrace, which is just about to celebrate its 10th anniversary in the wild. The screencast has some additional examples of DTrace's power on its own, as well as diving into the DTrace/Oracle Database 12c synergy.
There's more, of course. Over on the OTN Garage blog, Rick Ramsey has put together a nice compendium of ways the OS makes the database scream, and Ginny Henningsen's written an article on the same topic. And, we've also got an OTN page that digs further into Oracle Database / Oracle Solaris optimizations.