485.You want to back up your 100-GB database on a remote tape device. You are required to ensure that
minimum network bandwidth is consumed while transferring the backups to the tape device.
The current consumption of your CPU is approximately 40 percent.
Which type of backup should you perform?
A. standard backup set
B. image copy
C. compressed backup
D. user-managed backup
Answer: C
答案解析：
使用压缩备份，可以节省空间，减小带宽。
COMPRESSED |
Enables
binary compression.
RMAN compresses the data written into the backup set to reduce the overall size of the backup set. All backups that create backup sets can create compressed backup sets. Restoring compressed backup sets is no different from restoring uncompressed backup
sets.
RMAN applies a binary compression algorithm as it writes data to backup sets. This compression is similar to the compression provided by many media manager vendors. When backing up to a locally attached tape device, compression provided by the media
management vendor is usually preferable to the binary compression provided by BACKUP AS COMPRESSED BACKUPSET. Therefore, use uncompressed backup sets and turn on the compression provided by the media management vendor when backing up to
locally attached tape devices. You should not use RMAN binary compression and media manager compression together.
Some CPU overhead is associated with compressing backup sets. If the target database is running at or near its maximum load, then you may find the overhead unacceptable. In most other circumstances, compressing backup sets saves enough disk space to be worth
the CPU overhead.
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