OCP-1Z0-052-V8.02-11题

11. Identify the memory component from which memory may be allocated for:

1: Session memory for the shared server

2: Buffers for I/O slaves

3: Oracle Database Recovery Manager (RMAN) backup and restore operations

A.Large Pool

B.Redo Log Buffer

C.Database Buffer Cache

D.Program Global Area (PGA)

Answer: A

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12231785

大型池

数据库管理员可以配置称为“大型池”的可选内存区，以便为以下对象提供大型内存分配：

• 共享服务器的会话内存和Oracle XA 接口（在事务处理与多个数据库交互时使用）

•I/O 服务器进程

• Oracle DB 备份和还原操作

通过从大型池中为共享服务器、Oracle XA 或并行查询缓冲区分配会话内存，Oracle DB 可以主要使用共享池来缓存共享SQL，并避免由于收缩共享SQL 高速缓存而导致的性能开销。

此外，用于Oracle DB 备份和还原操作、I/O 服务器进程以及并行缓冲区的内存以数百KB 的缓冲区进行分配。与共享池相比，大型池可以更好地满足此类大型内存请求。

大型池没有LRU 列表。它与共享池中的保留空间不同，后者与从共享池中分配的其它内存使用相同的LRU 列表。

The large pool is an optional memory area intended for memory allocations that are larger than is appropriate for the shared pool.

The large pool can provide large memory allocations for the following:

• UGA for the shared server and the Oracle XA interface (used where transactions interact with multiple databases)

• Message buffers used in the parallel execution of statements

• Buffers for Recovery Manager (RMAN) I/O slaves

By allocating session memory from the large pool for shared SQL, the database avoids performance overhead caused by shrinking the shared SQL cache. By allocating memory in large buffers for RMAN operations, I/O server processes, and parallel buffers, the large pool can satisfy large memory requests better than the shared pool.

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e40540/memory.htm#CNCPT1233

The large pool is different from reserved space in the shared pool, which uses the same LRU list as other memory allocated from the shared pool. The large pool does not have an LRU list. Pieces of memory are allocated and cannot be freed until they are done being used. As soon as a chunk of memory is freed, other processes can use it.