Explanation:
The verification of the existence of a matching primary key before adding a foreign key can consume a significant amount of time. Oracle9i addresses this performance problem by enabling you to cache the first 256 primary keys; this improves the time it takes to verify the existence of a primary key and therefore enhances performance when adding multiple foreign keys.
Incorrect Answers:
1: Oracle9i will cache the first 256 primary keys, not 32.
2: Oracle9i will cache the first 256 primary keys, not 128.
4: Oracle9i will cache the first 256 primary keys, not 512.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 260-261
Chapter 5: Language Enhancements
Oracle 9i New Features, Robert Freeman, p. 167
Chapter 6: Oracle9i SQL, PL/SQL New Features

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