单项选择题 Consider the following command：  Backup database plus archivelog delete input；  How many backup sets would be created by this command if the following were true：（）  Control-file a NN uto backups were enabled.  NN The size of backup sets was not restricted.  NN One channel was allocated.

单项选择题 WhattypeofbackupisstoredinaproprietaryRMANformat？（）

单项选择题 Howisblock-changetrackingenabled？（）