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
同661题：http://blog.csdn.net/rlhua/article/details/12165227
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