Before you perform the database update you should shut down the Application Server Instance using that Application Server Database.

Updating a database might take somewhere from a few seconds to a few hours depending on the number of updates steps performed and depending on the amount of data in your database. Therefore be sure to plan for a longer downtime of your Application Server.

Updating the structure of a database is a process that can fail for many reasons and may leave the database in an inconsistent state. Therefore it is absolutely mandatory to have a backup of the database you update before starting the update process.