OCP-1Z0-053-200题-85题-661

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本文详细解释了在使用RMAN进行数据库备份时，如何通过设置FILESPERSET和MAXOPENFILES参数来控制备份过程中文件的读取数量及多路复用级别。通过具体的例子展示了不同配置下备份操作的行为变化。

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QUESTION 85

View the Exhibit and examine the output.

You execute the following RMAN command to perform thebackup operation:

RMAN> RUN {

ALLOCATE CHANNEL c1 DEVICE TYPE disk MAXOPENFILES 8;

BACKUP DATABASE FILESPERSET 4;

}

What is the multiplexing level in the preceding backup process?

A. 4

B. 8

C. 7

D. 0

Answer: A

Explanation/Reference:

Section: Backup, Recovery & Recovery Manager (RMAN)

The MAXOPENFILES parameter of ALLOCATE CHANNEL or CONFIGURE CHANNEL defines how many

datafiles RMAN can read from simultaneously. The basic multiplexing algorithm is as follows:

- Number of files in each backup set

This number is the minimum of the FILESPERSET setting andthe number of files read by each channel. The

FILESPERSET default is 64.

- The level of multiplexing

This is the number of input files simultaneously read and then written into the same backup piece. Thelevel of

multiplexing is the minimum of MAXOPENFILES and the number of files in each backup set. The

MAXOPENFILES default is 8. Suppose that you back up 12 datafiles with one channel when FILEPERSET is

set to 4. The level of multiplexing is the lesser of this number and 8. Thus, the channel simultaneously writes

blocks from 4 datafiles into each backup piece. Nowsuppose that you back up 50 datafiles with one channel.

The number of files in each backup set is 50. The level of multiplexing is the lesser of this number and 8. Thus,

the channel simultaneously writes blocks from 8 datafiles into each backup piece.

http://www.filibeto.org/sun/lib/nonsun/oracle/11.1.0.6.0/B28359_01_200708/backup.111/b28270/rcmtunin.htm

Tuning RMAN Performance