OCP-1Z0-052-V8.02-16题

16. Note the following functionalities of various background processes:

1: Record the checkpoint information in data file headers. CKPT

2: Perform recovery at instance startup. SMON

3: Cleanup unused temporary segments. SMON

4: Free the resources used by a user process when it fails.

5: Dynamically register database services with listeners.

6: Monitor sessions for idle session timeout.

Which option has the correct functionalities listed for a background process?

A.Archiver Process (ARCn): 1, 2, 5

B.System Monitor Process (SMON): 1, 4, 5

C.Process Monitor Process (PMON): 4, 5, 6

D.Database Writer Process (DBWn): 1, 3, 4

Answer: C

 

答案解析：

参考：http://blog.csdn.net/rlhua/article/details/12232625

进程监视器进程(PMON) 在用户进程失败时执行进程恢复。PMON 负责清除数据库缓冲区高速缓存以及释放该用户进程使用的资源。例如，它重置活动事务处理表的状态，释放锁，并且从活动进程列表中删除该进程ID。

PMON 定期检查分派程序和服务器进程的状态，并重新启动任何已停止运行（但并非Oracle DB 故意终止）的分派程序和服务器进程。PMON 还将有关实例和分派程序进程的信息注册到网络监听程序。

与SMON 一样，PMON 定期检查以查看是否需要执行；如果其它进程检测到需要该进程，也可以调用它。

 

Process Monitor(PMON):performs process cleanup when a user process fails

The process monitor (PMON) monitors the other background processes and performs process recovery when a server or dispatcher process terminates abnormally. PMON is responsible for cleaning up the database buffer cache and freeing resources that the client process was using. For example, PMON resets the status of the active transaction table, releases locks that are no longer required, and removes the process ID from the list of active processes.

PMON also registers information about the instance and dispatcher processes with the Oracle Net listener . When an instance starts, PMON polls the listener to determine whether it is running. If the listener is running, then PMON passes it relevant parameters. If it is not running, then PMON periodically attempts to contact it.

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