Tools and Utilities - Expert Oracle RAC Performance Diagnostics and Tuning - page 196

Conclusion
One of the main aspects of an application performing well is to ensure that the persistence layer, which comprises
SQL statements accessing the database, performs well. While there are several products available from various
vendors today, Oracle provides several options for tuning SQL queries. Under this category the EXPLAIN PLAN,
SQL_TRACE, event 10046, and event 10053 were discussed with trace outputs.
The OWI, an internal mechanism that provides time-based wait statistics, was discussed in principle; the wait
interface that comprises GV$SESSION_EVENT , GV$SYSTEM_EVENT , GV$SESSION_WAIT , GV$SYSSTAT , and GV$SESSTAT was
discussed in length. The discussion also included a few examples regarding analyzing this data for improving the
performance of the system. More details on the wait interface are forthcoming in Chapter 17.
RAC comprises many instances of Oracle with one common database. While the ultimate goal of the enterprise
system is to have the clustered solution perform well, this cannot happen unless the individual instances perform well.