Before you move the RDS DB instance to a new network, configure the new VPC, including the security group inbound rules, the subnet group, and the route tables. When you change the VPC for a DB instance, the instance reboots when the instance moves from one network to another. Because the DB instance isn't accessible while the instance is being moved, change the VPC during a scheduled maintenance window.

You can't change the VPC for a DB instance if:

• The DB instance is in multiple Availability Zones. Convert the DB instance to a single Availability Zone, and then convert it back to a Multi-AZ DB instance after moving to the new VPC. For more information about converting instances, see
  High Availability (Multi-AZ).
  Note: You can't change a DB subnet group to a Multi-AZ configuration. By default, the Amazon Aurora storage is Multi-AZ—even for a single instance—so you can't change the VPC for Amazon Aurora. To change the VPC for an Amazon Aurora instance, create a DB snapshot, and then
  restore the instance from a DB snapshot in the new VPC.
• The DB instance is a read replica or has read replicas. Remove the read replicas, and then add read replicas after the DB instance is moved to the new VPC.