Performance Tuning - Question 023

Which of these are true statements about tuning the dictionary cache? (Choose two.)

A . The DBA should perform DDL during peak activity hours.

B. The algorithm that manages data in the shared pool prefers to keep dictionary cache data over library cache data.

C . The algorithm that manages data in the shared pool prefers to keep library cache data over dictionary cache data.

D. When using sequences, the CACHE option improves dictionary cache performance.

Explanation:

Answer B and D: It is important to remember that dictionary cache misses are more expensive than library cache misses, so the algorithm that manages the shared pool prefers to keep objects in the dictionary cache. If the library cache statistics look good, that means the library cache is sized appropriately, and infers that the dictionary cache is sized appropriately. If you do not use the CACHE option on a sequence, each call to NEXTVAL creates a get in the dc_sequences dictionary cache item. Also, the DBA should perform DDL during off-peak hours.