DB Instance Upgrades and Maintenance
Changes to a DB instance can occur when you manually modify a DB instance, such as when you upgrade the DB engine version, or when Amazon RDS performs maintenance on an instance. This section provides information on how you can upgrade a DB engine version and information on process Amazon RDS uses to perform required maintenance.
You can choose to upgrade a DB instance in some cases when a new DB engine version is supported by Amazon RDS. Each DB engine has different criteria for upgrading an instance and what DB engine versions are supported. See the following section for your DB engine for more information on upgrading a DB engine version.
Periodically, Amazon RDS performs maintenance on Amazon RDS resources, such as DB instances. Maintenance most often involves updates to the DB instance's operating system (OS).