Explanation:
DB_BLOCK_CHECKING parameter in the parameter file set to TRUE will force Oracle to check Oracle database data blocks for corruption.
Incorrect Answers:
1: Verification of structural integrity of Oracle database files is done with the DBVERIFY utility. DBVERIFY is a utility that verifies the integrity of a datafile backup or production file. It can be used either to verify that a backup is usable, to verify the usability of a production database, or to diagnose where corruption is suspected on a datafile or backup. But DBVERIFY is Oracle utility, not a parameter in the parameter file.
2: DBMS_REPAIR is a package to detect data corruption, but it's not a parameter in the parameter file.
4: There is no VALIDITY_STRUCTURE parameter in the Oracle parameter file.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 659-663
Chapter 14: Database Failure and Recovery

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