1Z0-062 Question #202: Real Exam Question with Answer & Explanation

The correct answer is C: All redo log entries in the current log are applied to data files until the checkpoint position is. During Oracle instance recovery, only online redo log entries from the last checkpoint position forward through the current log are applied - archived logs and inactive logs are not required.

Question

Which statement is true about redo log files during instance recovery?

Options

AAll current, active, and inactive redo logs are required to complete instance recovery.
BAll redo log entries in the current and active logs are applied to the data files to reconstruct
CAll redo log entries in the current log are applied to data files until the checkpoint position is
DAll current, online, and archived redo logs are required to complete instance recovery.

Explanation

During Oracle instance recovery, only online redo log entries from the last checkpoint position forward through the current log are applied - archived logs and inactive logs are not required.

Common mistakes.

A. Inactive redo logs contain changes that have already been written past the checkpoint to data files, making them unnecessary for instance recovery; only current and active online redo logs are required.
B. Applying all entries in both current and active logs regardless of checkpoint would be incorrect - only entries at or after the most recent checkpoint SCN are needed, as earlier changes are already durably reflected in the data files.
D. Archived redo logs are used for media recovery when restoring from a backup, not for instance (crash) recovery, which is entirely handled by the online redo log groups.

Concept tested. Oracle instance recovery using online redo logs and checkpoint position

Reference. https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/oracle-database-instance.html

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