Modifies the configuration of your Reserved Instances, such as the Availability Zone, instance count, or instance type. The Reserved Instances to be modified must be identical, except for Availability Zone, network platform, and instance type.

For more information, see Modifying Reserved Instances in the Amazon EC2 User Guide.

We are retiring EC2-Classic. We recommend that you migrate from EC2-Classic to a VPC. For more information, see Migrate from EC2-Classic to a VPC in the Amazon Elastic Compute Cloud User Guide.