12. Which is the correct description of a pinned buffer in the database buffer cache?
A.The buffer is currently being accessed.
B.The buffer is empty and has not been used.
C.The contents of the buffer have changed and must be flushed to the disk by the DBWn process.
D.The buffer is a candidate for immediate aging out and its contents are synchronized with the block
contents on the disk.
Answer: A
答案解析：
Every buffer has an access mode: pinnedor
free(unpinned). A buffer is "pinned" in the cache so that it does not age out of memory while a user session accesses it. Multiple sessions cannot modify a pinned buffer at the same time.