Which of the following will cause an immediate DB instance reboot to occur?

You need to change some settings on Amazon Relational Database Service but you do not want the database to reboot immediately which you know might happen depending on the setting that you change.

Which of the following will cause an immediate DB instance reboot to occur?
A . You change storage type from standard to PIOPS, and Apply Immediately is set to true.
B . You change the DB instance class, and Apply Immediately is set to false.
C . You change a static parameter in a DB parameter group.
D . You change the backup retention period for a DB instance from 0 to a nonzero value or from a nonzero value to 0, and Apply Immediately is set to false.

Answer: A

Explanation:

A DB instance outage can occur when a DB instance is rebooted, when the DB instance is put into a state that prevents access to it, and when the database is restarted. A reboot can occur when you manually reboot your DB instance or when you change a DB instance setting that requires a reboot before it can take effect.

A DB instance reboot occurs immediately when one of the following occurs:

You change the backup retention period for a DB instance from 0 to a nonzero value or from a nonzero value to 0 and set Apply Immediately to true.

You change the DB instance class, and Apply Immediately is set to true.

You change storage type from standard to PIOPS, and Apply Immediately is set to true.

A DB instance reboot occurs during the maintenance window when one of the following occurs:

You change the backup retention period for a DB instance from 0 to a nonzero value or from a nonzero value to 0, and Apply Immediately is set to false.

You change the DB instance class, and Apply Immediately is set to false.

Reference: http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Troubleshooting.html#CHAP_Troubleshooting.Security