Explanation:
The V$ROWCACHE view statistics is used to tune dictionary cache. You calculate the hit ratio using the formula : sum (GETS - GETMISSES) / sum (GETS) * 100. An ideal hit ratio for dictionary-cache activity is 99 percent or higher.
Incorrect Answers:

1: The V$ROWCACHE view is not used to tune the library cache. The V$LIBRARYCACHE view is used for this purpose.
3: With V$ROWCACHE you can tune only data dictionary cache, not entire shared pool cache.
4: This view is not used to determine the hit ratio for large objects such as PL/SQL packages.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 852-858. Chapter 18: Tuning Memory and Operating System Use

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