Finding and fixing database problems, and optimizing performance and managing service levels are key responsibilities for every DBA. While the Oracle database has many tools for diagnosing and troubleshooting, and most DBAs have their cadre of scripts, the vast majority of DBAs responsible for sizable and or critical database estates depend on Enterprise Manager to simplify and speed their efforts.

Thanks to Timothy Mooney for this great article: Maximizing Database Performance: Best Practices for Mission Critical Systems