Performance Tuning - Question 046

Which of these statements is true about latches?

A. While one process holds a latch on a memory structure, no other process can access or scan the memory structure.

B . All latches are in one of two modes: scan or lock.

C . Scan latches are used on the LRU lists in the buffer cache.

D . One process can scan a memory structure while another process holds a latch on the structure.

Explanation:

Answer A: Latches, with only a few exceptions, are exclusive. The structure of a latch is simple; it does not support queueing or sharing. The idea is that a latch will only be held briefly. Scanning a memory structure requires a latch, since because otherwise the memory structure could be changed by another process, invalidating the first scan.