Explanation:
You can use the GATHERING_MODE => 'END' option to end system statistics collection, the GATHERING_MODE => 'START' option to enable manual statistics collection. The INTERVAL option is used to specify a fixed interval to collect statistics. The routine allows the optimizer to consider a system's CPU and I/O utilization and performance.
Incorrect Answers:
5: The routine does not allow the optimizer to invalidate existing cached plans.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 220-222
Chapter 4: Performance and Scalability Enhancements
Oracle 9i New Features, Robert Freeman, p. 180-185
Chapter 6: Oracle9i SQL, PL/SQL New Features

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