Performance Tuning - Question 002

Which of these will cause performance degradation on full-table scans?

A. Empty or underused blocks below the high watermark.

B . Empty blocks above the high watermark.

C . Performance indexes on nonpimary key columns.

D . Empty blocks in the region of a segment that have never been used.

Explanation:

Answer A: Empty or underused blocks below the high watermark will be visited by every full-table scan, thus degrading performance. If full-table scans are used frequently, then consider reorganizing the table to eliminate the empty and underused blocks.