单项选择题

You notice a performance change in your production Oracle 12c database. You want to know which change caused this performance difference.
Which method or feature should you use?（）

A. Compare Period ADDM report
B. AWR Compare Period report
C. Active Session History (ASH) report
D. Taking a new snapshot and comparing it with a preserved snapshot

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多项选择题
Which three features work together, to allow a SQL statement to have different cursors for the samestatement based on different selectivity ranges?（）

A. Bind Variable Peeking
B. SQL Plan Baselines
C. Adaptive Cursor Sharing
D. Bind variable used in a SQL statement
E. Literals in a SQL statement
多项选择题
You notice a high number of waits for the db file scattered read and db file sequential read events in the recent Automatic Database Diagnostic Monitor (ADDM) report. After further investigation, you find that queries are performing too many full table scans and indexes are not being used even though the filter columns are indexed. Identify three possible reasons for this.（）

A. Missing or stale histogram statistics
B. Undersized shared pool
C. High clustering factor for the indexes
D. High value for the DB_FILE_MULTIBLOCK_READ_COUNT parameter
E. Oversized buffer cache
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