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Question 13: View the Exhibit and examine the output.You execute the following RMAN command to perform the backup 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
Correct Answer: A
Explanation:
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 and the 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.
The level 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. Now suppose 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/b2
8270/rcmtunin.htm Tuning RMAN Performance.
