This concise book contains detailed information about Oracle internals -- information that's not readily available to Oracle customers. It lays a foundation for advanced performance tuning of the Oracle database. Based on Oracle8i release 8.1, the book describes many of the secrets of Oracle's internal services: data structures, algorithms, and undocumented Oracle system statistics. Main topics include: Waits - how Oracle processes communicate via semaphores, and how to use the Oracle wait statistics to identify the source of performance problems. Latches - how they keep multiple processes from inspecting protected data structures at the same time, and how to examine and control latch behavior and statistics. Locks - how they work with latches to protect data structures (locks allow multiple sessions to share resources in some cases), and how locks affect performance. There is also a detailed discussion of instance locks, which are used in parallel server environments. Memory - how Oracle uses memory (e.g., the various elements of the System Global Area), and how Oracle dynamically allocates and manages memory. Oracle8i Internal Services is aimed especially at administrators and developers who need detailed internal information to do advanced performance tuning. The book will expand your repertoire of tuning solutions and troubleshooting techniques by explaining how you can use Oracle's hidden parameters and undocumented system statistics to best advantage. NOTE: The author has collected the scripts he has developed for tuning and analysis into a toolkit (known as APT, for Advanced Performance Tuning). These scripts access the Oracle X$ tables directly and provide information not otherwise available. The scripts are available to readers for free from the O'Reilly web site.