OCP-1Z0-052-V8.02-17题

17. Note the functionalities of various background processes:

1: Perform recovery at instance startup. SMON

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

3: Cleanup the database buffer cache when a process fails. PMON

4: Dynamically register database services with listeners. PMON

5: Monitor sessions for idle session timeout. PMON

6: Cleanup unused temporary segments. SMON

7: Record the checkpoint information in control file. CKPT

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

A.Checkpoint (CKPT): 1, 2, 5

B.System Monitor (SMON): 1, 6

C.Process Monitor (PMON): 4, 6, 7

D.Database Writer (DBWR): 1, 3, 4

Answer: B

参考：16题http://blog.csdn.net/rlhua/article/details/12253391

以及进程介绍：http://blog.csdn.net/rlhua/article/details/12232625

系统监视器进程(SMON) 在实例启动时执行恢复（如果需要）。

SMON 还负责清除不再使用的临时段。如果在实例恢复过程中由于文件读取或脱机错误跳过任何已终止的事务处

理，则SMON 将在表空间或文件重新联机时恢复这些事务处理。

SMON 定期检查以查看是否需要该进程。其它进程在检测到需要SMON 时也可以调用它。

The system monitor process (SMON) is in charge of a variety of system-level cleanup duties. The duties assigned to SMON include:

• Performing instance recovery, if necessary, at instance startup.In an Oracle RAC database, the SMON process of one database instance can perform instance recovery for a failed instance.

• Recovering terminated transactions that were skipped during instance recovery because of file-read or tablespace offline errors. SMON recovers the transactions when the tablespace or file is brought back online.

• Cleaning up unused temporary segments. For example, Oracle Database allocates extents when creating an index. If the operation fails, then SMON cleans up the temporary space.

• Coalescing contiguous free extents within dictionary-managed tablespaces.

SMON checks regularly to see whether it is needed. Other processes can call SMON if they detect a need for it.

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e40540/process.htm#CNCPT1254