Home » Oracle » 1z0-062 v.2 » 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.
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
Correct Answer: ACD
Explanation/Reference:
D: DB_FILE_MULTIBLOCK_READ_COUNT is one of the parameters you can use to minimize I/O during table scans. It specifies the maximum number of blocks read in one I/O operation during a sequential scan. The total number of I/Os needed to perform a full table scan depends on such factors as the size of the table, the multiblock read count, and whether parallel execution is being utilized for the operation.
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