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
Explanation:
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.