1Z0-053 争议题目解析134

1Z0-053 争议题目解析134

考试科目：1Z0-053
题库版本：V13.02

题库中原题为：

134.You are managing an Oracle Database 11g database. You want to take a backup on tape drives of
the USERS tablespace that has a single data file of 900 MB. You have tape drives of 300 MB each. To
accomplish the backup, you issued the following RMAN command:
RMAN>BACKUP
SECTION SIZE 300M
TABLESPACE users;
What configuration should be effected to accomplish faster and optimized backups by using the above
command?
A. The SBT channel must be configured, with the default parallelism setting for the SBT device set to 1.
B. The COMPATIBLE initialization parameter for the database instance must be set to at least 10.0.
C. The SBT channel must be configured, with the parallelism setting for the SBT device set to 3.
D. The SBT channel must be configured, with the MAXPIECESIZE set to 300 MB.
Answer: D

争议点：
根据网上Riveore对这道题的解析：应该是C选项。
原文地址：http://blog.csdn.net/rlhua/article/details/14228765

答案解析：
参考：http://docs.oracle.com/cd/E11882_01/backup.112/e10643/rcmsynta007.htm#RCMRF90025
根据Note: You cannot use SECTION SIZE with MAXPIECESIZE or with INCREMENTAL LEVEL 1.这句话，说明D错误
根据RMAN channels can process each step independently and in parallel，应该选择C，可以并行备份。

SECTION SIZE sizeSpec Specifies the size of each backup section produced during a data file backup.
By setting this parameter, RMAN can create a multisection backup. In a multisection backup, RMAN creates a backup piece that contains one file section, which is a contiguous range of blocks in a file. All sections of a multisection backup are the same size. You can create a multisection backup for a data file, but not a data file copy.
File sections enable RMAN to create multiple steps for the backup of a single large data file. RMAN channels can process each step independently and in parallel, with each channel producing one section of a multisection backup set.
If you specify a section size that is larger than the size of the file, then RMAN does not use multisection backup for the file. If you specify a small section size that would produce more than 256 sections, then RMAN increases the section size to a value that results in exactly 256 sections.
Depending on where you specify this parameter in the RMAN syntax, you can specify different section sizes for different files in the same backup job.
Note: You cannot use SECTION SIZE with MAXPIECESIZE or with INCREMENTAL LEVEL 1.

初步结论：
上面Riveore的解析已经很清楚了，C选项。