The main causes of planned downtime are routine operations, periodic maintenance, and upgrades.
Routine operations occur for both the database and applications. Routine operations on the database include backup, performance management, and user and security management. Routine operations on an application includes batch processing.
Periodic maintenance occurs on the database, applications, the operating system, middleware, and the network.
Upgrades are done on the hardware, the operating system, the database, middleware, applications, and the network.