Oracle OCP 1Z0 053 Q348(RMAN Minimize Load)

348.What does the minimize load database parameter mean when backing up a database?
A. RMAN will attempt to make the backup run as fast as possible without any IO limitations.
B. RMAN will automatically restrict the number of channels in use to one.
C. RMAN will spread the backup IO over the total duration stated in the backup command.
D. RMAN will skip any datafile that currently is involved in an IO operation. RMAN will retry backing up the
datafile later and an error will be raised at the end of the backup if the datafile cannot be backed up.
E. Datafiles will be backed up; those having the lowest current number of IO operations will be backed up
first.
Answer: C

使用了minimize load, RMAN會監測備份時的資源消耗，並定時估計以當前的速度備份要花費多長時間。如果備份估計的完成時間在備份視窗結束之前，RMAN就會降低備份速度以充分利用整個可用的備份視窗。
這降低了與備份有關的資料庫的負載。

BACKUP 
  DURATION 4:00 PARTIAL 
  MINIMIZE LOAD 
  DATABASE 
  FILESPERSET 1;

In Example 9-5, RMAN monitors the progress of the running backup, and periodically estimates how long the backup will take to complete at its present rate. If RMAN estimates that the backup will finish before the end of the backup window, then it slows down the rate of backup so that the full available duration will be used. This reduces the overhead on the database associated with the backup.

官方文件：https://docs.oracle.com/cd/B28359_01/backup.111/b28270/rcmbckad.htm

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